Melt 1 tablespoon of butter in a large pan until it froths. Add bacon and stir and sauté until crisp, approx. 5 to 6 minutes. Remove the bacon with a ladle, drain on paper towel and set aside.
Place the mushrooms in the pan and cook in the dripped fat over medium heat, stirring occasionally until they brown slightly and some of the liquid evaporates (this takes about 8 minutes). Transfer the mushrooms to a bowl with the remaining cooking liquid and set aside.
Melt and froth the remaining 2 tablespoons of butter, add onion and garlic, season with salt and pepper and sauté until translucent for about 3 minutes. Add carrot, celery and potato, season with salt and pepper, mix with onions and garlic and cook for approx. 7 minutes, stirring occasionally. Add cooked wild rice and thyme and mix in, dust with the flour and continue cooking, stirring constantly, until a fine layer of flour has formed around wild rice and vegetables and a light film has formed on the bottom of the pan (approx. 2 minutes).
Add the cooked mushrooms, bay leaf and broth and bring to a boil over medium heat. Reduce heat and cook vegetables for about 15 minutes. Stir in milk and cream, add pepper and simmer the soup for about 10 minutes until it thickens slightly, stirring occasionally.
Finally season the soup with lemon juice, salt and pepper, remove the bay leaf and serve garnished with the fried bacon.