1 Bring the white wine to the boil, stir in the mussels and steam for 3 minutes with the lid on. Scoop out the mussels and add the stock to the wine. Set aside.
2 Heat the oil and butter in a separate pan and fry the garlic, spring onions, fennel, chilli and tomato paste for a minute or two until fragrant. Stir in the rice and cook for 2 minutes until it’s coated with the mixture. Stir the stock, a ladle-full at a time, into the rice. Wait until the stock is completely absorbed before adding more; stir occasionally. After about 15 to 20 minutes, the rice should be al dente. Avoid the last bit of stock at the bottom of the pot in case there’s sand or shell residue in it. If you wish to rinse the mussels beforehand, don’t do so excessively as you’ll spoil the seafood flavour.
3 Season the rice with salt and pepper, then stir in the cooked mussels and sour cream, along with a sprinkling of fennel leaves. Remove from the heat and allow to stand for 2 minutes before dishing up.