Melt butter in a microwave

Place melted butter in a bowl

Add sugar and whisk well.

Add egg, whisk again

Add the milk, whisk to have a homogeneous mixture

Add the sifted flour with baking powder and a pinch of salt, give a few lashes without working the dough too much.

Place the dough in a pastry bag, and fill 6 medium muffin cups halfway.

Add the teaspoon of Nutella, and fill with the remaining dough

With a wooden skewer, make movements in the dough to give a marbled effect to the muffins

Bake in an oven preheated to 200°C for 5 minutes, then lower the temperature down to 175°C and bake between 15 and 20 minutes, until you have a nice brown colour in the muffins.