Saute onion in a little butter until golden. Add the meat and stir until browned . Dilute tomato paste with a little water and add to meat. Add wine, cover and simmer for about 30 minutes, until meat is done and sauce is thick.
Remove from heat, allow to cool. Once cool, mix in grated cheese, egg, blending well.
Cut filo into strips of desired width. Brush each strip with melted butter using a pastry brush. Place one heaping teaspoon of filling on end of strip. Turn strip over filling to form a triangle. Continue folding from side to side until end of strip is reached. Continue to make triangles until all filling and strips are used. Place triangles close together, seam side down, on a greased cookie sheet.
Bake in a preheated 350 degree oven until golden brown. To bake frozen meat filled triangles, place immediately in a preheated 400 degree oven and bake until golden brown.