In a bowl cream the butter and sugar until light and fluffy. Add the egg and flavor and stir. Add the flour and baking soda and mix well until a very soft dough is formed.

Keep in the freezer for 10mins. Bring it out and mix again then make a small ball,flatten it and use one of your kitchen measuring spoon set to make a small hole in the middle and fill it with nutella.repeat process until you're done. Arrange on a line baking tray and baked in a preheated oven until the desired browness is achieved.

My own cookies have cracks because I didn't bake them immediately.after moulding them I had to keep them for over an hour before baking. I guess the delay is what caused the cracks. But they were super delicious. Also,you can bake for less than the duration I've given. That depends entirely on the Temperature of your oven.