Melt the butter

• Put the butter in a microwave-safe bowl.
• Microwave until melted.

Mix the wet ingredients

• Add the sugar to the melted butter.
• Add the egg yolk and the vanilla extract.
• Mix everything together until combined.

Add the flour

• Add the flour, sifted or not.
• Mix until it forms a soft dough.

Add the chocolate

• Fold the chocolate pieces into the dough.
• Add any extra toppings if wished.

Microwave the cookie

• Microwave the cookie in the bowl until set.