Whip the eggs with the sugar until pale, then stir in the melted butter and yogurt.

At this point, sift the flours, baking powder, lemon zest and vanilla seeds and add them to the batter, stirring just enough to mix everything. Add the chocolate chips and mix.

Divide the batter into 12 muffin moulds lined with baking cups and bake in the hot oven (180 C) for about 25 minutes, until puffed and golden.