Here's the recipe:
For the dough you'll need
1 litre mashed potato
1 egg
1 dl flour
1 teaspoon salt
For the filling:
some cooked rice (1/2 litre water, 1.5 dl rice, 1/2 teaspoon salt)
a little melted butter

Mash, and add the egg, flour and salt. Mix together, to make a very soft dough.

Then make the dough into a round stick. Cut into 10 pieces, and pat flat, in a rough half-moon shape.

Take your cooked rice, and add a little melted butter. Place a teaspoon of rice on each half-moon.

Fold the dough over, patting gently down. Use an upturned mug to shape into a half-moon (from the offcuts, you should get another 5 vatruskas).

Bake in an oven at 300 degrees (or the hottest it will go) for 10-15 minutes.

Once they're done, brush with a little melted butter. Then top with munavoi (egg butter - yes, there's lots of butter involved here), and scoff...

...very quickly, before the small child eats them all!
