Preheat oven to 350 degrees F. Grease your mini muffin tin.
Cream butter and both sugars in bowl until light, smooth and fluffy! Beat in eggs and vanilla until fully incorporated. Gradually add dry ingredients (flour, salt, baking soda) until all the flour is mixed in!
Put a hunk of dough in each mini muffin tin and bake for 10-12 minutes, until golden brown but not too dark around the edges.
When done, remove from oven and let sit for about 2 minutes. Then make wells for the nutella with a tart shaper or a similar object or a spoon. Add 1 dollop of Nutella to each cup – it will start to melt quickly so you can swirl it around and make it nice and smooth.
Let cool 15-20 minutes in tin.