If using jarred grape leaves, separate them gently and rinse under hot water 2 to 3 times to wash off the brine. Trim any tough stems with scissors and set aside a few torn or small leaves to line the pot.

In a large mixing bowl, combine the rinsed rice, ground pork, ground beef, grated onion, grated tomato, tomato paste, mint, parsley, 3 tbsp of the olive oil, 2 tbsp of the lemon juice, cinnamon, salt and pepper. Mix with your hands until well combined.

Lay a grape leaf shiny side down on a cutting board, stem end toward you. Place 1 heaping tablespoon of filling near the stem end.

Fold the stem end and both sides over the filling, then roll away from you into a snug cylinder, like a small cigar. Don't roll too tight, since the rice will expand as it cooks. Repeat with the remaining leaves and filling, making about 40 rolls.

Line the bottom of a 28 cm / 11-inch heavy pot with the reserved torn leaves and a few lemon slices, to stop the rolls from sticking and scorching.

Arrange the koupepia seam side down in tight rows in the pot, stacking a second layer on top if needed.

Pour the remaining olive oil and lemon juice over the rolls, then add the water or stock until the liquid just covers the top layer.

Place a small heatproof plate directly on top of the rolls to keep them from unrolling as they cook.

Cover the pot and bring to a gentle simmer over medium heat, then lower the heat and simmer for 45 minutes, until the rice is tender and a roll cut in half shows no raw meat.

Turn off the heat and let the koupepia rest in the pot, still covered, for 10 minutes before lifting out.

Serve warm or at room temperature, with lemon wedges and a spoon of yogurt on the side.