In a food mixer with a paddle attachment, beat the butter, sugar and syrup together until light and fluffy.
Beat the egg in a separate bowl and mix in the vanilla paste. Add this to the beaten butter and sugar and mix.
Fold in all the remaining ingredients except the marshmallow pieces. Mix well to form a cookie dough.
Weigh out 40g balls of dough and place them on a glass baking tray lined with baking parchment. Flatten the dough balls slightly and leave enough room for them to spread.
Chill the cookie dough for at least an hour before baking in a preheated 180°C oven.
Bake for 15 minutes. Add a marshmallow to the centre of the cookie and bake for a further 5 minutes. Remove from the oven and let the cookies cool on a rack.
Get 3 kitchen lab beakers, and fill each with milk. Pierce a whole through each marshmallow cookie and insert straw.
16 cookies
20 minutes
