Preheat your oven to 190°C (375°F). While the oven heats, bring a large pot of water to a gentle boil. Slice the tops off the bell peppers about 1cm from the stem, and carefully remove the seeds and white membranes from inside. Set the tops aside — you can chop them finely and add to the filling later. Cue: the peppers should feel firm but hollow when you tap them gently.

Blanch the peppers for 4 minutes. Submerge the hollowed peppers in the boiling water, then reduce the heat to a simmer. After 4 minutes, they should look slightly brighter in colour and feel tender when you press the sides with a tongs. Cue: the peppers will release a sweet, steamed aroma and the skin will feel slightly softened but not splitting. Drain them upside-down on a clean tea towel to remove excess moisture.

Cook the filling base. Heat the olive oil in a large frying pan over medium-high heat. Add the diced onion and cook for 3-4 minutes until translucent and fragrant. Cue: the onion should sizzle gently and smell sweet, with edges turning golden. Add the minced garlic and cook for another 30 seconds until fragrant but not browned.

Brown the beef mince. Add the beef mince to the pan, breaking it apart with a wooden spoon. Cook for 5-7 minutes, stirring occasionally, until the meat is no longer pink. Cue: the sizzling will become more vigorous as moisture evaporates, and the meat will turn a rich brown colour with crispy edges forming on some pieces. Drain any excess fat if necessary, leaving about a tablespoon for flavour.

Build the sauce. Stir in the tomato purée, oregano, smoked paprika, and cumin. Cook for 1 minute until the spices become aromatic. Cue: the tomato purée will darken slightly and the pan will smell deeply savoury. Add the chopped tomatoes, beef stock, and cooked quinoa. Stir everything together, then reduce the heat to low. Simmer for 8-10 minutes, stirring occasionally, until the mixture thickens. Cue: the sauce should bubble gently and reduce until it coats the back of a spoon — no watery liquid should pool at the bottom of the pan. Season with salt and pepper.

Stuff the peppers. Arrange the blanched peppers upright in a baking dish that fits them snugly. Spoon the filling evenly into each pepper, pressing down gently to pack it in. Cue: the filling should mound slightly above the rim of each pepper — don't overfill, or the tops won't sit properly. If using cheese, sprinkle it over the tops now.

Bake until bubbling. Pour about 50ml of water or leftover beef stock into the bottom of the baking dish (this creates steam and prevents the peppers from drying out). Bake uncovered for 25-30 minutes. Cue: the cheese (if used) will be golden and bubbling, the peppers will look slightly wrinkled at the edges, and the filling will be steaming vigorously when you open the oven. Let them rest for 5 minutes before serving — this helps the filling set.