Bring a large pot of salted water to a boil. Add penne pasta and cook according to package directions, about 8-10 minutes, until al dente. Drain and set aside, keeping a little pasta water.

In a large skillet, melt 2 tablespoons of butter over medium heat. Add 2 minced garlic cloves and sauté for about 1 minute. Toss in 8 ounces of sliced mushrooms, cooking for 5-7 minutes until golden brown.

In a food processor, combine 1 cup of walnuts, 2 cloves of garlic, and 1/2 cup of grated Parmesan cheese. Blend while slowly drizzling in 1/2 cup of olive oil until creamy. Season with salt to taste.

Add the cooked penne to the skillet with mushrooms. Pour in walnut pesto and gently toss until well-coated. Add pasta water if the mixture seems dry.

Plate in warm bowls, garnishing with additional Parmesan or a poached egg if desired. Serve immediately.