Melt the butter in a skillet set over moderate heat. Add the onions, lower the heat and cook, stirring frequently, for 5 minutes, or until they are lightly colored.
Transfer them to a large bowl. Bring 2 c water to a boil in a saucepan set over high heat.
Stir in the rice, lower the heat and cook uncovered for 8 minutes, then drain through a sieve. Stir the rice, lamb, coriander, dill, peas, salt and pepper into the onions and stir all the ingredients together lightly but thoroughly.
Taste for seasoning. Bring 4 c water to a boil in a saucepan and drop in the grape leaves. Boil for 3 to 4 minutes, uncovered, then drain. Flatten them out.
Put each leaf the inner side up. Place 1 tb stuffing in the center of each leaf.
Roll leaves, covering stuffing from sides like an envelope.
Arrange the rolls, seam-side down, in a pan just large enough to hold them in one layer.
Pack them in side by side so that they retain their shape while cooking.
Pour in the chicken stock and bring to a boil.
Cover the casserole tightly, lower the heat, and stew for about 45 minutes.
Serve the grapes rolls with a bowl of yogurt sprinkled with cinnamon.