Place flour, sugar, salt, & yeast in large bowl.

Stir in warm milk, followed by oil, egg yolks & vanilla.

With electric mixer, beat for 2 minutes on high speed.

Stir in enough flour until the dough holds together.

On a floured surface, knead 50 turns, cover with plastic and let rest 10 min.

If using custard filling, make it now so it can cool. (see recipe below)

Line a large baking sheet with parchment paper.

On a floured surface, roll dough 1/2-inch thick. Cut circles using a 2 1/2 -inch round cutter, dipped in flour. Re-roll scraps.

Place mounds on baking sheet, cover with a towel, and let rise in a warm spot about 45 minutes. (1 hour at room temp.) During this time, preheat oven to 375° F.

When paczki are puffy, but not necessarily doubled in size, bake for 10 minutes.

Melt butter and place 1/3 cup sugar in a plastic produce bag. Lay down some wax paper to save cleanup.

Remove paczki immediately from pan to wax paper. Brush each one while warm (top & sides) with melted butter and roll in bag to coat with sugar.

For jam, fill warm or cooled paczki using a pastry bag with a long tip, pushing into the side, or cut a slit in the side and insert filling with a spoon. For custard, cool paczki before filling. All paczki are best served right away.

Custard Filling:

In a small saucepan, combine 1/4 cup sugar + 4 teaspoons cornstarch. Slowly stir in 1 cup low fat or whole milk + 1 egg yolk. Bring to a boil. Cook & stir about a minute. (it thickens more as it cools) Spread onto a dinner plate and let it stand, undisturbed, to cool thoroughly before using - refrigerate if necessary.