Preheat oven to 350°.
Chop mushrooms into 1/2" pieces. Place in a bowl with the garlic cloves and toss with 2 tbsp. olive oil and 1 tsp. salt. Spread in a single layer on a baking sheet and place in the oven on the middle rack roast for 12 minutes.
While the mushrooms are roasting, place the remaining tbsp. of olive oil in the bottom of a large pot and add the minced shallot. Cook over medium heat until the shallot softens and starts to brown around the edges, about 4-5 minutes.
Stir in flour and cook, stirring constantly for another minute. Then add roasted mushrooms and garlic as well as the rosemary and thyme. Continue cooking and stirring until herbs become fragrant, 1-2 minutes.
Stir in 1/2 cup of the stock and cook just until it is well incorporated and begins to thicken. Then stir in the rest of the stock.
Using a stick blender, carefully blend the soup until the desired consistency is reached. I like to leave little chunks of mushroom, but you can blend it silly smooth if that's what you prefer.
Bring soup to a boil, then reduce the heat and simmer for 30 minutes, stirring occasionally.
If you want a creamed soup, stir the cream into slowly simmering (not boiling) soup, and continue to stir occasionally until heated through.
Serve topped with grated pecorino cheese, a dollop of sour cream, or bacon and croutons!
