Preheat your oven to 190°C (fan 170°C). While it heats, rinse the brown rice under cold water until the water runs clear — you'll see the cloudy starch disappear, which stops the rice turning gluey.

Sauté the aromatics. In a large ovenproof skillet or frying pan, heat the olive oil over medium heat until it shimmers. Add the diced onion and cook for 4-5 minutes, stirring occasionally, until it turns translucent and smells sweet. Stir in the garlic and cook for 30 seconds until fragrant.

Cook the vegetables. Add the carrots, courgette, and red bell pepper to the pan. Cook for 5-6 minutes, stirring often, until the courgette softens and the carrots begin to look glossy. The pan should smell earthy and slightly sweet.

Make the creamy sauce. Sprinkle the flour over the vegetables and stir constantly for 1 minute — the mixture will look clumpy and pale. Slowly pour in the milk while whisking, then add the stock. Keep stirring until the sauce thickens enough to coat the back of a spoon, about 3-4 minutes. Stir in the dried thyme, smoked paprika, and a generous pinch of salt and pepper.

Add the rice and peas. Tip in the rinsed brown rice and frozen peas, then stir until everything is evenly distributed. The mixture will look quite liquid — that's exactly what you want, as the rice needs that moisture to cook properly.

Bake covered. Transfer the mixture to a 9x13 inch baking dish if your pan isn't ovenproof. Cover tightly with aluminium foil and bake for 30 minutes. You'll know it's ready when the kitchen fills with a warm, herby aroma and the rice is tender when you peek under the foil.

Add cheese and finish. Remove the foil carefully (watch out for the steam — it's hot). Sprinkle the grated cheddar evenly over the top, then return to the oven uncovered for 10-12 minutes. The casserole is done when the cheese is bubbling and golden in patches, and the edges look slightly crispy.

Rest before serving. Let the casserole sit on the counter for 5 minutes. This allows the sauce to settle into the rice so each spoonful holds together rather than turning soupy.