Prepare the filling following the vanilla pastry cream recipe. To fill the doughnuts, you need only half of the recipe – so, halve all the ingredient quantities.

You can prepare the pastry cream a day or two in advance, keeping it in the fridge in a closed air-tight container until needed. It's best to cover the pastry cream in the container with a piece of cling film (plastic wrap), so that it’s in direct contact with the surface – this will prevent any skin formation.

On the day you intend to make and fill the doughnuts, take the pastry cream out of the fridge and bring it to room temperature. Initially, the cream will look rather rubbery and firm, but just give it a thorough whisk (either by hand using a balloon whisk, with a had mixer fitted with the double beaters or with a stand mixer fitted with the whisk attachment) until it’s once again silky-smooth.

Activate the yeast: In a small bowl, mix together the yeast, 10g (about 1 tablespoon) sugar and warm milk. Set aside for 10-15 minutes, or until the mixture starts frothing.Tip: If using instant yeast, you don’t need to activate it. Instead, just add it straight to the dry ingredients along with the sugar. Add the milk that would be used in activating the active dried yeast to the dry ingredients along with the psyllium gel and egg.

Make the psyllium gel: In a separate bowl, mix together the psyllium husk and cold water. After about 30-45 seconds, a gel will form.

For the following steps, I recommend using a stand mixer fitted with the dough hook attachment. You can also make the dough by hand, but the mixer makes it much easier and results in a smoother dough.

In the bowl of the stand mixer, whisk together the tapioca starch, millet flour, sorghum flour, xanthan gum, salt, baking powder and the remaining sugar.

Make a well in the middle of the dry ingredients and add the egg, yeast mixture and psyllium gel.

Knead the dough until smooth and all the ingredients are evenly incorporated, about 5-10 minutes. Use a rubber spatula to occasionally scrape along the sides and bottom of the bowl to prevent any dry patches of unmixed flour.

Add the butter and knead until it’s fully incorporated. The final dough will be very soft and sticky.Tip: If your dough is very soft and sticky at this point, that's perfectly okay! The next chilling step will firm it up and make it much easier to handle.

Transfer the dough into a lightly oiled bowl, cover the bowl with cling film (plastic wrap) and chill in the fridge for at least 1-2 hours.Tip 1: Chilling cools down and sets the butter in the dough, which in turn makes the dough firmer and easier to handle and shape into the individual doughnuts. It also gives the gluten free flours time to properly hydrate (that is, to absorb the moisture in the dough), which also makes the dough less sticky.Tip 2: You could even chill the dough overnight, and then shape, proof and fry the doughnuts the following day!

Once chilled, divide the dough into 8 equal pieces (each piece should weigh about 88g). Tip: I recommend using a digital food scale to get all pieces the same weight, as that will ensure that they all cook at the same rate and will therefore prevent any doughnuts from being undercooked.

On a lightly floured surface, shape the pieces of dough into balls, as you would dinner rolls or burger buns, and finally flatten them.To shape each piece of dough into a flattened ball:First, flatten the piece of dough. Then, take the corners and bring them in towards the middle, until you get something resembling a pouch. Pinch the ends together. Turn the piece of dough upside down, so that the seams face downwards. Form your hand into a “claw” over the piece of dough and move it in a circular motion on the surface (this will essentially rotate the dough in place, which will help to form a perfectly round ball and also seal the seams together). Finally, gently flatten the ball until it’s about 1-1¼ inch (2.5-3cm) thick at the centre point (take into account that it will have rounded edges and it will therefore be thinner towards the edge), and about 3 inches (7.5cm) in diameter.Repeat with the rest of the dough pieces.Tip: By shaping the doughnuts by hand into flattened balls (as opposed to cutting them out with a round cookie cutter), the final fried doughnuts have a nicer, rounder shape.

Place the doughnuts on individual squares of parchment/baking paper on a large baking sheet. Tip: These squares of parchment paper will make placing the proofed doughnuts into the frying oil much easier and pretty much stress-free.

Proof the doughnuts in a warm place for about 1½ hours or until about doubled in volume. Lightly cover them with a sheet of cling film (plastic wrap) to prevent them from drying out during proofing.Tip: If your kitchen is on the cold side, you can proof them in a lukewarm oven (the ideal proofing temperature is around 79ºF/26ºC).

After the doughnuts have been proofing for about 1 hour, you can start setting up your “frying station”. For this, you can use a large heavy-duty pot or deep pan, a large cast iron pot or a deep fryer if you have one. If you’re using a pot or a deep pan, make sure that you fill it with enough oil so that the oil is at least 2 inches (5cm) deep.Tip: The best oil for frying is one that’s neutral in flavour and has a high smoking point. I prefer to use sunflower oil, but you can use your favourite frying oil instead (so long as it fulfils those requirements).

Heat the oil to 320-330ºF (160-165ºC), and make sure to maintain this temperature throughout the frying process (you might need to adjust your stove’s heat to maintain the oil temperature at the correct temperature range).It’s best to use a digital food thermometer (or a candy thermometer or a deep-fry thermometer) to make sure that your oil is at the right temperature.Tip: In this temperature range, the doughnuts will get beautifully golden brown by the time they’re fully cooked through and they’ll absorb only a very minimal amount of oil (pretty much negligible). A lower oil temperature can leave them pale and can also result in them absorbing some of the oil, which can make them greasy. A higher oil temperature will cause them to brown too much and too quickly.

Once the doughnuts have doubled in volume, carefully place them into the hot oil. Use the squares of parchment paper to help you lower the doughnuts into the oil. After 10-15 seconds, you can use kitchen tongs to remove the squares of parchment paper out of the oil.The number of doughnuts that you’ll be able to fry at the same time will depend on the size of your pot, pan or fryer. Don’t crowd them together too much.

Fry the doughnuts on this first side for about 2½ minutes or until deep golden brown, then flip them over.

Fry them on the other side for a further 2½ minutes or until deep golden brown.

Use a slotted spoon to remove the doughnuts out of the oil and onto a large plate or wire rack lined with paper towels. Make sure to drain your doughnuts properly before placing them onto the paper towels. Tip 1: I like to cover them with a layer of paper towels on top as well, just to absorb any oil on top of the doughnuts.Tip 2: Note that the doughnuts will initially have a crisp crust immediately out of the hot oil, but the crust will soften after a minute or two.

Allow the doughnuts to cool until they’re warm or lukewarm before filling.

To fill the doughnuts, first make a hole in the doughnuts – I like to use a long thin knife for this, but you can use everything from scissors to skewers. Making a hole will make filling the doughnuts much easier.

Make sure that your pastry cream is smooth and pipeable. Give it another whisk if necessary.Transfer it to a piping bag fitted with a round piping tip (alternatively, you can just cut off the end of the piping bag and use it without a piping tip).

Fill the doughnuts until the pastry cream starts coming out of the hole – that tells you that the doughnuts are filled to their maximum capacity. I filled each doughnut with about 45g of pastry cream.

Place the chopped dark chocolate into a heat-proof bowl.

In a saucepan over medium-high heat or in the microwave, heat the double/heavy cream until it only just comes to a boil.

Pour the hot cream over the chocolate and allow to sit for 2-3 minutes, then stir together until smooth and glossy.

Dip the top of each doughnut into the chocolate ganache and shake off any excess.

Allow the chocolate ganache to set at room temperature for 10-15 minutes before serving.

The gluten free Boston cream doughnuts are best served while they’re still slightly warm or within about an hour of frying. However, you can keep them for up to five hours either lightly covered with paper towels or a clean tea towel, or in a closed container.