3: In an oven-proof dish, spread the mushrooms in an even layer and drizzle olive oil over them. Stir to distribute the oil. Scatter the shallott over, salt and pepper, then add 1 bayleaf (cut into pieces) and 1 sprig rosemary.
4: Cook in the oven for 20 to 30 minutes, until the mushrooms have given off all their liquid and are starting to brown. Remove and discard the rosemary and bits of bayleaf.