What's a recipe for a mashed-potato filled roll of eastern european cuisine?!

Those are potato piroshki!

Basically a bun dough, with potato filling.
There are lots of variations as to what to add to the potatoes -

Dough
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Active dry yeast - 1 packet(1/4 oz / 7g)
All purpose flour - 3 cups
Salt - 1 teaspoon
Sugar - 3 tablespoons
Milk - 1/2 cup
Water - 1/4 cup
Oil - 1/4 cup
Eggs - 2

Dissolve the yeast in 1/4 cup lukewarm water and 1 teaspoon sugar and leave it aside for about 10 minutes till it turns foamy..
Combine flour, salt and sugar and mix them thoroughly..
Fold in the yeast mixture, milk, eggs (1 egg+1 egg white) and oil and knead it for around 5 minutes till you get an elastic soft dough..
Cover the dough with a kitchen towel and leave it aside in a warm place until it doubles in size..This might take around one hour..

Meanwhile prepare the potato filling.
Boil two or three large potatoes til tender, and mash.
Add salt, pepper - and I would add sauteed onions and dill - you can add what seasonings you like.
You could also add cheddar cheese, or dry cottage cheese if you wanted.

Flatten out a little ball of dough, add about 2 spoons filling, and wrap around, seal edges with a little water.
Preheat the oven to 350 degree F and in the meantime brush the dough with the yolk of one egg..This gives the nice golden colour to the Piroshki..
Bake for 30 to 35 minutes until they turn nice golden colour..

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There are some variations here - the dough is a baking powder dough, instead of yeast-based
http://docs.google.com/viewer?a=v&q=cach…

Ingredients And Procedures
1 md Onion

2 c Potato buds

1 1/2 c Peas and Carrots

2 Green Chillies

1 ts Lemon Juice

1 c Gram flour

1/2 ts Mustard seed

pn Turmeric 1/2 ts Baking powder

1/4 Inch Ginger

1 sm Bunch Coriander leaves

2 ts Salt

Oil The filling is prepared as follows: 1. Mix potato buds and 1/2 tsp of salt with 1 cup of hot water

2. Chop ginger, chillies, coriander leaves, and onion finely

3. Heat oil (about 5 table spoons) and add mustard seeds

4. Add chopped ingredients and fry till onions are brown

5. Add carrots, peas, turmeric and 1 tsp of salt and cook on low

heat for about 10 minutes. 6. Add potato (now mashed) and fry for 5 minutes.

7. Remove from heat and add lemon juice and let it cool

The batter is prepared as follows: Combine gram flour, 3 tbsps of oil, 3/4 cup water, 1/2 tsp salt, the baking powder and mix thoroughly After batter is prepared, make small balls out of the filling and roll them in the batter. Then fry in hot oil. You will get about 20-30 small bondas.

http://cooking.7sk.org/Bonda_with_Instant_Mashed_Potato/257.html

My friend, you probably had something that was unique to Bubba; many things were made back in the day out of the necessity to feed one's self and be full on what was available.
Now what it sound like is you had potato pie of some type.
Mashed potatoes that were laid on a rolled out pie crust then the pie crust was folded around the potatoes and then baked.
I have had a version of this but a variance on the Welch Pastie; just mashed potatoes and a little cheese mixed in instead of the of meat and veggies that normally go in it.
Sorry, wish I could be more help to you.
The only thing I could find that had mashed potatoes and bread was this recipe.
http://momofukufor2.com/2010/06/mashed-p…

2 Dozen chicken wings

1/2 ts Coconut extract

4 ts Curry powder

6 tb Melted butter

1 c Milk

2 c Instant mashed potatoes

3 tb Sweetened, flaked coconut

2 Cloves garlic, minced

Cut tips off wings. In a large bowl, combine milk, extract and wings. Stir to mix well. Marinate at least 2 hours (or overnight). In another bowl, combine potatoes, curry and cocoanut. Take wings out of marinade and roll in potato mixture. Place slightly apart on well greased cookie sheets. Combine butter & garlic. Drizzle over wings. Bake, uncovered, at 375 degrees until browned - 45 minutes.

http://cooking.7sk.org/Coconut_Curried_Wings/69.html

My mother made a bread with mashed potatoes mixed in with the flour etc, that's as close as I can get.
You would have to wing it from there.