Very soft, easy to make, I really like the texture of the preparation, it is soft and light, of course the taste is delicious 
A crazy recipe!
I leave you with the pictures!
For this recipe you will need:
2 eggs
90g of sugar
85g melted butter
120ml of milk
160g flour
40g unsweetened cocoa powder
1 packet of baking powder
Pinch of salt
100g chocolate chips
METHODE
In a bowl, mix the eggs and sugar well, then add the melted butter, mix, after pouring the milk, mix again, then add the flour, the cocoa, the baking powder, the sifted salt, mix the preparation well, finally add the chocolate chips mix for the last time.
Pour the preparation into the cassettes, put a few pieces of dark chocolate on the muffins.
Preheat the oven to 200 degrees for 5 minutes.
Then lower the temperature to 180 degrees for 15 to 16 minutes.
At the exit of the oven add some chocolates on the muffins (like me), for more delicacy 
Test it you will love it!