Step 1:

Preheat the oven to 170 c and arrange the muffin cases on the muffin tray

Sieve the flour, cocoa powder, baking powder and salt in a bowl

Step 2:

In a jug mix together the eggs, milk, melted butter, sugar and vanilla extract until it is well combined

Add the egg mixture to the bowl little by little mixing up these two mixtures. Using a spatula scrape the mixture from the sides of the bowl and mix until all the ingriedients are well mixed

Step 3:

Add the chocolate chips to the mixture and mix again.

spoon the mixture into the muffin cases until two thirds and bake in the oven for 30 minutes, or until the sponge bounces back when touched

Step 4:

Leave the muffins to cool slightly in the tray before moving them to a cooling rack

Step 5: The Science Behind It

They use baking powder which is a blend of acid and alkalis. These create carbon dioxide bubbles when liquid and heat are added.

Most baking powders are double acting, that is they produce an initial set of gas bubbles upon mixing and then a second set during the baking process.

When using baking powder, add this ingriedient last as it will begin to create CO2 as soon as it comes into contact with moisture