Tip the rice into a bowl. Cover with cold water. Whisk the rice for 1-2 mins till the water turns cloudy (this is the starch). Drain the rice. Rinse under cold water.
Tip the rice into a small pan. Pour in 400ml boiling water. Add a pinch of salt. Cover. Bring to the boil. Turn the heat right down. Gently simmer for 8 mins till the water has been absorbed and the rice is tender. Take off the heat. Leave to steam for 5 mins to finish cooking the rice.
Whilst the rice is cooking, thickly slice the mushrooms. Peel and thinly slice the onion. Peel and grate or crush the garlic. Finely shred the sprout tops.
Heat a pan then add 1 tbsp olive oil. Throw in the beef stir-fry strips. Cook for 2-3 mins till browned. Remove from the pan into a bowl using a slotted spoon.
Keeping the pan on the heat, add the mushrooms and onions. Cook for 4 mins till softened and juicy. Add the garlic and fry for 1 min. Tip the beef back into the pan along with any resting juices.
Add 1 tsp smoked paprika and stir well to coat. Pour in the crème fraîche and set the heat to low.
Transfer the sprout tops to the pan with the beef and mushroom stroganoff. Cook together for 3 mins till wilted.
Taste and season the stroganoff. Add a little more paprika if you like. Serve the stroganoff with the steamed rice. Cut the lemon into wedges and squeeze over to taste.