Preheat the oven to 200°C.
Sauté the onion in half the butter in an ovenproof pan until softened.
Stir in the rice, frying gently for one minute before adding hot stock, seasoning, and bay leaf.
Boil the mixture, cover with buttered greaseproof paper and a lid, and bake for 15 minutes.
Remove the bay leaf, stir in remaining butter, fluff the grains, and keep warm.
Season beef strips with paprika, salt, and pepper.
Flash-fry beef in oil until rare, then drain in a colander, reserving the juices.
Sauté shallots and mushrooms in butter for one minute.
Cook in the tomato purée, then add vinegar and simmer until evaporated.
Add white wine, reduce by half, then pour in double cream and boil.
Return the beef and juices to the pan and warm gently without boiling.
Garnish with pickles, sour cream, parsley, and paprika, then serve with rice.