1. In a large skillet over medium heat, melt 1 TBSP butter with 2 TBSP olive oil.
2. Add onions, 1/2 tsp. salt, and sugar. Stir until browned and fragrant, about 10 minutes. Remove from pan and set aside.
3. Add the remaining 1 TBSP butter and 1 TBSP olive oil to the skillet.
4. Stir in the mushrooms and 1/4 tsp. salt. Continue cooking over medium heat until mushrooms are tender and browned, about 5 minutes.
5. Add the cooked onions, parsley, 1/4 tsp. salt, and pepper. Keep warm until the pasta is ready.
6. Prepare the pasta in a large pot, according to package directions. Drain, reserving 3/4c of the water, and return to pot.
7. To the pasta pot, add 1/2c of the pasta water, the mushroom mixture, 1 TBSP olive oil, goat cheese, and Parmesan. Add extra pasta water, if necessary.
8. Garnish with extra Parmesan cheese and parsley.