Squash and Sausage Shepherd's Pie

I got this from Better Homes and Gardens, the October 2012 issue.  I've gotta say, I am not usually a fan of shepherd's pie, but this was great and different and felt...fresher...than the usual type.  And two of my four kids gobbled it down, which was amazing.  Ben called this recipe a "double smiley face."  I don't have individual casserole dishes, so I used my own large casserole dish. 

Squash and Sausage Shepherd's Pie

1 butternut squash, peeled, seeded, and cut into chunks
5 Tbsp butter, softened
1/4 cup grated Parmesan cheese
1 tsp. salt
1/2 tsp. ground black pepper
1 lb. sweet Italian sausage or ground beef (I couldn't find any sweet Italian sausage that wasn't in casings, so I had to just cut and peel the casings off, breaking the meat apart when I cooked it.)
3 Tbsp. olive oil
1 medium onion, chopped
8 oz fresh, sliced mushrooms
3 cloves garlic, minced
1 cup beef broth
1/2 of a 28-oz can crushed tomatoes (about 1 1/2 cups)
1 Tbsp. snipped fresh or 1 tsp. dried rosemary
1 tsp. Worcestershire sauce
1 cup frozen peas and carrots
shaved Parmesan cheese (optional)
sliced green onion (optional)

1.  Preheat oven to 425 degrees.  Lightly coat a large casserole dish (or six 10- to 12-oz. individual casseroles) with nonstick cooking spray.
2.  In a large pan, cook squash in lightly-salted boiling water, covered, for 15-17 minutes or until tender when pierced with a fork.  Drain; return to pan.  Mash with butter, Parmesan, 1/2 tsp. of the salt, and 1/4 tsp. of the pepper; set aside.
3.  Put 2 Tbsp. olive oil in a large skillet; cook sausage in it over medium high heat, breaking up and cooking until no longer pink. Remove cooked meat from skillet.
4. In same skillet, heat 1 Tbsp. oil over medium heat.  Add onion and mushrooms; cook, stirring occasionally, until tender, about 4 to 5 minutes.  Add garlic; cook 2 minutes more.  Stir in broth, crushed tomatoes, rosemary, and Worcestershire sauce.  Bring to boiling, reduce heat to medium and simmer until thickened, about 5 minutes.  Stir in meat, peas and carrots, remaining 1/2 tsp. salt, and 1/4 tsp. pepper; cook 2 minutes.  If using small individual casseroles, divide mixture among them.  If using one large casserole dish, pour the whole thing in the bottom.  Spread top with butternut squash.  Place on a large baking sheet.
5.  Bake, uncovered, for 20 minutes or until top is lightly browned. Top with shaved Parmesan and green onion, if desired.  Makes 12 servings.