Peel onion and garlic. Chop the onion finely. Chop the garlic. Heat 1 tablespoon of oil in a wide saucepan. Fry onion, garlic and rice in it until transparent. Gradually deglaze with stock and simmer for about 20 minutes, stirring regularly.
In the meantime thaw the peas. Clean, clean and halve the mushrooms. Wash and halve the tomatoes. Heat 1 tablespoon of oil in a pan. Fry the mushrooms until golden brown all around. Peel 20 g parmesan in slices, grate the rest of the parmesan.
Stir butter and grated parmesan into the risotto. Add mushrooms, peas and cherry tomatoes and fold in. Wash the thyme and shake dry. Pluck the leaves, except for a few for garnishing, from the stems and sprinkle them on the risotto.
Season to taste with coarse pepper and arrange on plates garnished with remaining thyme and parmesan slices.