Here is one recipe for a filled Russian Bread--the recipe is from the Frugal Gourmet On Our Immigrant Ancestors-- He has a recipes in the book for Russian Round and Dill Onion Breads too.
PAGACH
Makes 1 1arge loaf, enough for 8 servings
This recipe certainly points to the cleverness of the cooks from the Ukraine. The dish is a bread and potato or cabbage pie. That's it; no meat at all. The results are unusually delicious.
THE DOUGH
2 1/2 - 3 cups all-purpose flour
1 cup warm water (105°)
1 package quick-rising yeast
l/2 teaspoon salt
TOPPING
Salad oil
Additional salt or garlic salt
Dissolve the yeast in the warm water (105°). Add the salt and 2 1/2 cups flour. Knead until smooth, adding more flour as needed if the dough is still too sticky. Place the dough on a plastic countertop and cover it with a stainless-steel bowl. Allow it to rise until double in bulk. Meanwhile, make the filling (recipes follow).
Punch down the dough. Divide it into 2 parts. Roll the dough out into a rectangle, 18 inches long by 12 inches wide. Place the filling on one side of the rectangle, being careful to leave a margin of about 2 inches from the edges. Fold the other half of the dough over the filling so that you now have a turnover, 9 inches by 12 inches. Pat the top of the dough down lightly into the filling. Carefully pinch the edges together. Spread the salad oil on top and sprinkle generously with the salt or garlic salt. Place on a greased baking sheet. Let rise until double in bulk. Bake in a preheated 400° oven for 30 minutes, or until golden brown.
PAGACH AND CHEESE POTATO FILLING
Boil peeled potatoes, about 1 1/2 pounds, drain and mash with a little butter and milk. Add grated sharp Cheddar cheese to the potatoes and cool (the more cheese, the tastier). Taste for salt and black pepper. Thls is a great filling for Pierogi or Pagach.
PAGACH CABBAGE FILLING (Sweet Cabbage Filling)
Cook 1 large peeled and sliced onion in 1/2 to 3/4 cup oil until soft. Add shredded green cabbage (medium head) and salt and freshly ground black pepper to taste. Cover and cook until the cabbage is soft. Drain the excess oil. This makes a good filling for Pagach or Haluski .