I made the cookies yesterday adn they turned out great except for the spices which I haven't gotten right yet.
As far as I know this is pretty close to the original recipe

100 gm butter
75 gm sugar
50 gm molasses
2 tbsp. water

2 1/2 cup flour
5 tsp. baking powder
pinch salt
1 tsp cinnamon
pinch cloves
pinch nutmeg

Cream butter sugar and molasses.
Add water.In a separate bowl, sift dry ingredients and then slowly incorporate into butter mixture.
Leave in the fridge overnight (for the spices)
Preheat oven to 175*C and roll out cookies to about 5 mm thick and cut into shape then lift onto lightly greased cookie sheets. Bake for about 10 minutes

This is the recipe for normal speculaas. There's a filled speculaas in Holland too which is more cakey and has a filling of almond paste