Heat the oven to 170 degrees. Stir the self-raising flour, oat flour, stevia, coconut sugar, gingerbread spices, cinnamon, baking powder and a pinch of salt together in a bowl.
Add the cold margarine, vanilla extract, and milk and knead into a firm ball. Do not knead too long, because the dough should not get too hot.
Line a baking tray with a piece of baking paper. Turn the dough into small balls (around 1 cm) and place them on the baking tray. Flatten them slightly.
Put the gingerbread cookies in the oven for about 30 minutes. When they come out of the oven they will still feel a bit soft but when they have cooled down they will become crispy.