Heat teh oil in a large, heavy-based pan with a lid. Gently cook the onion and bacon until the onion and bacon is tender and the bacon fat has run out.
Stir in the rice and garlic and cook over a high heat for 2-3 minutes, until the rice is well coated.
Add the dried mushrooms and their liquid, the fresh mushrooms, half the stock, the oregano or thyme and seasoning. Bring to a boil, then reduce the heat to low. Cover tightly and leave to cool.
Check the liquid and if dry, add more liquid as required until the rice is cooked, but not mushy. Just before serving, stir in the butter, white wine, tomatoes and olives and check the seasoning. Serve hot, garnished with thyme sprigs.