In a large mixing bowl, combine 1 cup of warm milk, 2 tablespoons of active yeast, and 2 tablespoons of sugar. Let it bloom for about 5 minutes until bubbly.

Add 4 cups of all-purpose flour, 2 beaten eggs, 4 tablespoons of melted butter, and 1 teaspoon of vanilla extract. Mix until a soft dough forms.

Knead by hand for about 5 minutes until smooth and elastic.

Place the kneaded dough into a greased bowl and cover with a damp cloth. Let it rise in a warm spot for 1-2 hours, or until it doubles in size.

Once risen, punch down the dough gently. Roll it out on a lightly floured surface to about 1/2 inch thick.

Using a round cutter, cut into circles and place them on a parchment-lined tray. Cover and allow to rest and rise for an additional 30 minutes.

Heat oil in a pot or deep fryer to 350°F (180°C). Fry donuts for about 2-3 minutes per side until golden brown.

Remove donuts and let drain on paper towels. Once cool, fill with prepared custard using a pastry bag.

Dust each warm donut with powdered sugar and serve immediately.