Place one large head of cored cabbage in a deep pot of boiling water to which salt has been added. Remove the leaves as they become soft. Cool and drain the leaves and remove any remaining core. Cut the leaves to the desired size (personally I cut them about 3" wide). Grease a casserole dish and place a few leaves of cabbage to line it. Put a tablespoon full of filling (filling recipe follows) into each leaf and roll it up tucking in the edges of the leaves as you roll. Arrange the holubtsi in layers, adding some fried onions and garlic (to taste, sauteed in olive oil) between the layers. When the dish is filled place extra prepared cabbage leaves over the top to prevent scorching. Cover and place in 325 degree oven for 1 1/2 to 2 hrs or until both the cabbage and filling are tender. For a nice variation you could also use grape or beet leaves. Also, you could pour some tomato juice over the top to add flavor.
FOR THE RICE FILLING: Wash rice well. Add water and stir in salt. Bring to boil and cook for one minute. Stir and cover. Turn down heat and simmer until rice starts to get tender. Take off of heat and let stand covered until the rest of the water is absorbed. The rice at this stage will only be partly cooked. Saute chopped onion in olive oil and add to the rice. Season to taste. Cool and roll into cabbage.
FOR THE BUCHWHEAT FILLING: Brown groats very lightly in the oven. Place in pot with boiling salted water. Add 4 tbsp olive oil. Cook until water is absorbed. Cover and bake in a 350 degree oven for 30 minutes. After baking allow the buckwheat to cool. Saute chopped onion in 1 tbsp of olive oil. Add the sauteed onions to the cooked buckwheat. Cool and fill the holubtsi.