In the morning, feed your starter by combing the starter, flour, and water in a bowl and mixing it until well combined. Tip it into a clean jar or glass and let it double or triple.

Prepare the dough by mixing together all the dough ingredients and using your hands to form a sticky dough ball. Knead the dough on the bench for 5-8 minutes until you create a smooth ball.

Place the dough in a greased bowl and cover it. Let it ferment for 3 hours, ideally at room temperature between 23-25°C/74-77°F. If your room is cooler than this, leave it for 4 hours. The dough should be visibly puffier after the fermentation. Place the bowl, tightly covered in the fridge overnight.

In the morning, mix 1 ½ tablespoons flour and 250g butter. Spoon the mix onto parchment paper and place another sheet on top. Roll the butter into a rectangle of about 15 x 20cm (6 x 8 inches). Place the butter in the fridge for around 10-30 minutes so it is cold. Ensure it is cold but still pliable. Aim for the butter and the dough to be similar in consistency.

Take the dough from the fridge and roll it out on a floured bench into a 20x40cm(8x16 inch) rectangle.

Once the butter is cool again, place it in the middle of the dough. Bring the top of the dough down and the bottom of the dough up to meet in the middle, and tuck in the butter.

Turn the dough a quarter turn. Use a rolling pin to gently push on the dough to help disperse the butter. Roll this dough out into a 25x50cm (10x20-inch) rectangle, focusing on lengthening rather than making it wider. While rolling, dust the dough with flour to prevent it from sticking to the bench.

Brush away the excess flour from the dough. Fold the dough like a pamphlet by bringing the top third down to the middle and the bottom third up overtop.

Wrap the dough up tightly or place it in an airtight container with a lid and let the dough rest in the fridge for 30 minutes.

Turn the chilled dough 90 degrees and roll it out in front of you into a 25x50cm (10x20 inch) rectangle. At this point, you can cut off any scraggly edges, which will help give you more even layers later. Repeat the folding process. Cover and place it back in the fridge for 20-30 minutes.

Repeat this step once more. After this fold, chill the dough, tighly covered, for at least 2 hours.

Roll the chilled dough into a 28x60cm (11x24 inch) rectangle on a floured bench.

Mark 5cm (2 inches) marks along both lengths of the dough rectangle. Use a pizza cutter or large knife to cut triangles connecting the marks from the top to the bottom. A ruler can help keep your lines straight. There is a picture diagram of this in the above post.

Stretch the bottom of each triangle out a bit, then roll the triangles up tightly, starting from the bottom and rolling to the tip. You can bend the ends of croissants a little to make a crescent or leave them straight

Leave the rolled croissants to proof on parchment paper-lined trays for around 4-5 hours at a temperature between 23-25°C/74-77°F. They should become puffy and jiggle when the tray is gently shaken, and the layers in the croissant should be visible.

You can brush the croissants gently with water to stop them from drying out or create a humid and warm spot by placing them in a cold oven next to a cup of hot water. Ensure the butter in the croissants doesn't melt, or it will ruin the layers. Don’t place the cup of hot water underneath the tray of croissants, or it’ll make the bottom of the tray too warm. Baking

The croissants can be baked once puffed out or refrigerated if you want to bake them in the morning. The extended fridge time will increase the sour flavor.

Preheat the oven to 205°C/400°F.

In a small bowl, mix the egg and water. Brush the croissants with the egg wash using a pastry brush.

Bake the croissants for around 20 minutes until deeply browned.

Croissants are great served fresh on the day they are baked. The layers in the croissants will be most prominent if the croissant has cooled down to room temperature before slicing.