Add flour to a large bowl, form a hollow in the middle and crumble yeast into it.
Heat milk lukewarm to the touch (not hot) and pour into hollow. Add 1 tbsp of sugar and mix to combine until yeast has fully dissolved. Cover and allow to sit in a warm place for about 10 minutes.
Add all the other ingredients for the dough and knead with dough hooks of a hand mixer or use a food processor until you end up with a smooth dough. Cover and allow to sit in a warm place again for about 45 minutes until dough ball has doubled in size.
In the meantime, prepare filling (e.g. prepare pudding/ chocolate spread or fill pastry bag with jam etc.)
Knead dough with hands and form into 8 balls. Flatten out a little on a baking sheet, cover and allow to sit for another 10 minutes.
In the meantime, preheat oven to 360° F / 180° C (for baked donuts) or heat oil for frying.
Dampen surface of donuts with a tiny bit of water. Bake donuts for 15-17 minutes at 360° F (180°C).
Brush margarine on warm donuts and sprinkle with powdered sugar.
Heat oil to about 338° F(170° C). Monitor with a kitchen thermometer or stick the end of a wooden spoon into the oil - if you see bubbles form around the wood and they start to float up, the oil is ready for frying.
Place dough balls into oil (only two at a time or so to leave room for flipping). Fry until the bottom side is deep golden brown, about 1 minute, then flip to cook the other side for another minute or two.
Place fried donuts onto a plate that has been lined with a few layers of paper towels and sprinkle with powdered sugar.
Using a pastry bag with a pointed pastry tip, squirt the jam/ chocolate spread/ pudding sideways into the middle of each (still warm) donut.