Heat the olive oil in a casserole and soften the onions for about 15 minutes. Add the garlic, cook a further 5 minutes, then add the fresh mushrooms and let them sweat gently with the onions, stirring often so that they cook evenly. Drain the dried ceps, keeping their soaking liquid. Squeeze the water out of the soaked ceps and chop coarsely, then add to the other mushrooms.
Add the tomato, paprika and salt, and continue to cook gently. All this has to be done slowly, but you can do other things at the same time, as long as you stir it from time to time, to make sure it does not catch.
When everything is soft and jammy, add the 500ml liquid from the dried ceps – leaving the last dregs, as this is full of dirt from the mushrooms – and the stock, bring to the boil and cook for 15–20 minutes. Throw in the vermicelli and cook until the pasta is tender, 10–15 minutes. Serve with slices of fried bread or toast.