Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Line two baking trays with baking paper. For the dough mix 125 g butter, sugar and 1 pinch of salt with the whisks of the mixer until foamy.
Stir in the eggs one by one. Mix 300 g flour, baking powder, grated coconut, oat flakes and speculoos spice. First briefly stir in with the whisks and then knead into a smooth dough with floured hands.
Form the dough into balls of about 2 cm in size with floured hands. Place them on the trays with some distance between them. Press flat with a floured fork (approx. 3.5 cm Ø). Bake one after the other in a hot oven for about 10 minutes until golden brown.
Remove and let it cool down on a cake rack.
Break milk chocolate into pieces for the filling. Melt with 20 g butter in a hot water bath. Spread each 2 biscuits on the smooth side with some chocolate butter and put them together.