Bring a large pot of salted water to a boil. Add 8 ounces whole wheat penne and cook until al dente according to package instructions. Before draining, scoop out and reserve 1/4 cup of the pasta cooking water. Drain the pasta and set aside.
While the pasta cooks, heat 1 tablespoon extra virgin olive oil in a large skillet over medium-high heat.
Add 3 cloves minced garlic and 1/2 teaspoon red chili flakes to the hot oil and sauté about 30 seconds to 1 minute, until fragrant but not browned.
Add 1 pound shrimp (deveined, peeled, tails removed) to the skillet. Season with salt and black pepper to taste. Cook the shrimp 2–3 minutes, turning once, until pink and opaque. Remove the shrimp from the pan and set aside.
Add the remaining 1 tablespoon extra virgin olive oil to the same skillet. Add 2 cups sliced brown mushrooms, season with salt and black pepper to taste, and sauté about 5 minutes, until the mushrooms are softened and lightly browned.
Return the cooked shrimp to the skillet with the mushrooms. Add the cooked pasta, juice of 1 lemon, the reserved 1/4 cup pasta cooking water, 1/4 cup parsley (chopped), and 1/4 cup grated Parmesan. Toss over medium heat for 1–2 minutes, until everything is heated through and the sauce coats the pasta. Taste and adjust salt and pepper as needed.
Transfer to a serving dish and garnish with the remaining 2 tablespoons chopped parsley. Serve immediately.