Bring a large pot of salted water to a boil. Wash and dry all produce. Trim and thinly slice scallions, separating whites from greens. Trim and quarter mushrooms. Mince or grate garlic.

Heat a large drizzle of olive oil in a large pan over medium-high heat. Add mushrooms and cook, stirring occasionally, until browned and softened, 7-9 minutes. TIP: If pan seems dry, add another drizzle of olive oil.

Once water is boiling, add tortelloni to pot. Reduce heat to a simmer and cook until tender and floating to the top, 3-5 minutes. Turn off heat, leaving pasta in water.

Add garlic, scallion whites, half the Italian Seasoning, and 2 TBSP butter to pan with mushrooms. Continue to cook over medium-high heat, stirring, until scallions are softened and butter has melted, 1-2 minutes. Season with salt and pepper. Reduce heat to low.

Stir cream cheese, sour cream, stock concentrate, 1/4 cup pasta cooking water (1/3 cup for 4 servings), and 1 TBSP butter (2 TBSP for 4) into pan until thoroughly combined. Using a slotted spoon, gently transfer tortelloni to pan. (TIP: Add more pasta cooking water as needed to create a creamy sauce.) Gently stir to coat. Season with remaining Italian Seasoning, salt, and pepper.

Divide pasta between bowls. Sprinkle with Parmesan, scallion greens, and chili flakes, if desired.