Preheat oven to 300 degrees. Thinly slice mushrooms. Mince garlic. Halve, peel, and mince shallot. Strip thyme leaves off sprigs, then roughly chop. Finely chop parsley. Slice half the polenta into 1/2-inch rounds (save remainder for another use).

Heat a thin layer of olive oil in a large pan over medium-high heat. Once hot, cook polenta until golden brown, 2-3 minutes per side. Transfer to a baking sheet, and place in oven to keep warm.

Heat 1 TBSP butter in same pan over medium-high heat. Add mushrooms and toss until golden brown, 5-6 minutes. Season with salt and pepper. Remove from pan and set aside.

Heat a drizzle of olive oil in same pan over medium heat. Add shallots, thyme, and garlic. Cook until softened, 2-3 minutes, Add 1/2 cup water and stock concentrate. Bring to a boil, then reduce to a simmer until thickened, 2-3 minutes. Remove pan from heat, then stir in sour cream and mushrooms. Season with salt and pepper.

Toss arugula and pine nuts in a bowl with a large drizzle of balsamic vinegar and olive oil. Season with salt and pepper.

Plate polenta pancakes topped with mushroom gravy and Parmesan cheese. Sprinkle with parsley. Serve arugula salad on the side and enjoy!