Bring water and margarine to boil, turn off heat, mix in flour, let rest for 10 minutes then mix in eggs one at a time (using mixer).
Preheat oven to 400 F, line a baking sheet with parchment paper, drop a spoon of batter until all used-up. Bake for 20-25 minutes without opening the oven at all.
Meanwhile mix butterscotch pudding with potato/corn starch and flour, then add in milk, water, and eggnog, bring to boil until thickened. Turn off heat, stir until pudding cooled down a bit, place in a squirt-bottle, and chilled until pudding kind of
firm but still a little runny.
Take out pastry from the oven and make a couple of holes on each but using toothpick; place on cooling rack. When pastries are cooled, either slice the top or make a hole big enough to squirt in the pudding. Serve immediately.
If served the next day or not immediately, place filled pastries in the fridge.