1-1.5 lb ground beef
3 medium onions, finely grated, preferably in a food processor
1 1/2 tsp salt
~1/4 tsp pepper
~1 Tbsp mint
2-3 eggs
2 slices bread (soak in water or milk and then squeeze it out)
1/3 cup short grain rice
~3 Tbsp olive oil
1/2 lb (~30) grapevine leaves, fresh or from a jar (in brine)
1 Tbsp butter
juice of 2 lemons
Boil grated onions for ~15 min. Cool. In a bowl combine onions, 1 egg, salt, pepper, mint, bread, rice, 2 Tbsp olive oil, ground beef and knead (with your hands). Rinse grape leaves if from jar. Place the drained leaves on a clean surface, inner side up. Add ~1 Tbsp of meat filling (depending on leaf size) above the stem. Roll leaves into a cylinder, tucking in sides. Place into a pot, packing the rolls tightly. Fill pot with water, almost covering the top row of dolmades. Add ~1 Tbsp butter and 1 Tbsp olive oil. Bring to a boil and simmer covered for about 1 hour or till the grape leaves are tender. Try one to check tenderness.
Drain the broth from the pot (or remove dolmades, whichever is easier). Beat 1-2 eggs well in a separate bowl; stir in lemon juice. Slowly add some hot broth to the egg-lemon (avgolemono) sauce while stirring, then stir this mixture into the remaining broth in a small pot. Heat while stirring for 3-5 minutes until the sauce thickens. If the sauce is too thin (it must coat a spoon well), add cornflour or flour (first mixed with some water). Place dolmades in serving plate, pour the avgolemono sauce over it and serve.