Heat oven to 375°F (190°C). Put rice, 1 1/2 cups water and 1/4 teaspoon salt in a small saucepan. Bring to a boil, cover and cook over low heat about 15 minutes, or follow the rice package. Turn off the heat and stand covered 5 minutes, then fluff.

Arrange peppers upright with openings facing up in a large baking dish, using two dishes if necessary to avoid stacking. Add 1/2 cup water around the peppers, cover with foil and bake 15 minutes to begin softening them.

Meanwhile heat oil in a wide skillet. Soften onion 5 minutes, then brown beef 7–8 minutes. Add garlic, tomato paste and oregano and stir 1 minute. Add crushed tomatoes, remaining salt and pepper; simmer 8 minutes until thick rather than soupy.

Fold cooked rice and half the mozzarella into the beef mixture. Carefully remove foil from peppers, tilting it away from your face to release steam. Divide the filling among six peppers, mounding it gently without pressing hard. Top with remaining cheese.

Cover loosely and bake another 20 minutes, then uncover and bake 10–15 minutes, until peppers are tender to a knife and the filling reaches 165°F (74°C). Rest 5 minutes and sprinkle with parsley. One serving is one filled pepper; cooking rice and browning beef overlap the pepper pre-bake.