In a medium saucepan, heat the milk and vanilla on medium heat until it is just at a simmer - don't let it boil. You'll see a collection of tiny bubbles accumulating around the edge of the saucepan.

While the milk is warming, in a separate bowl, add the egg yolks, sugar, salt and cornstarch. Whisk them together until glossy and smooth.

Place the bowl on a dampened kitchen towel to stop it from slipping around for this next step. Once your milk is infused and hot, it’s time for tempering the eggs.

Add the hot milk mixture in a steady stream to the egg mixture while whisking vigorously. This step is to prevent the egg yolks from curdling.

Return the combined mixture to the saucepan over medium heat, whisking constantly until it starts to bubble.

Once it starts bubbling, it will begin to thicken. Keep it at a bubble don't stop whisking for 1 minute.

Take it off the heat and whisk in the butter until completely combined.

Pour the hot pastry cream into a clean bowl. If you want an extra silky smooth texture, you can push it through a fine mesh seive first

Lay a piece of plastic wrap directly onto the surface of the custard to avoid a skin forming and let it come to room temperature. Chill it in the refrigerator until completely cold.

When ready to use, give it a whisk to loosen it up again as it will get very thick in the fridge. Crème pâtissière can be stored in the refrigerator in an airtight container for up to 3 days.