Preheat oven to 180°C.
Place rice into simmering basket and rinse under running tap. Insert into the Thermomix bowl and add a litre of water over the top. Steam 15 min/100°C/speed 3.5
In a hot pan, with a splash of EVOO, cook onion until soft, add garlic and cook for 2 minutes. add mince and cook through.
Add tomato paste, tin tomato, oregano, chilli flakes, salt and pepper and cooked rice. Let simmer for 20 minutes, until slightly reduced.
Pour marinara sauce into the bottom of a Dutch oven with lid.
Stuff the peppers carefully with the rice mixture, filling each one as full as possible. Stand each one up in the sauce, shoulder to shoulder, inside the Dutch oven. Cover and roast for 45 minutes or until well cooked and fragrant.
Serve immediately with a dollop of sour cream and basil leaves.