Heat a drizzle of olive oil in a large paella pan, frying pan or wok. Add mushrooms and cook until golden brown and their water has evaporated. Add onion and soften for 5 mins. Add bell pepper, chilli, garlic, turmeric and paprika. Cook until fragrant.
Add rice and cook, stirring constantly, until rice is translucent. Add wine and cook until completely evaporated. Add stock- the liquid should just cover the rice. Cook, without stirring, adding more stock if needed to keep rice moist while cooking, until rice is al dente and all liquid is absorbed, 15–20 minutes. (Shake pan after adding more stock to distribute evenly.)
Just before the rice is fully cooked add the mussels, ensuring that most of them are covered by the rice and cover with a lid. Cook for 2-3 minutes, or until the mussels open. Discard any that do not open.
Taste for seasoning and then scatter with fresh mirco herbs. Serve in the pan to keep warm alongside fresh lemon wedges.