Easy Cheese Tortellini Alfredo

Ingredients

• 2 packages (9 ounces each) refrigerated cheese tortellini
• 1/2 cup chopped onion
• 1/3 cup butter, cubed
• 1-1/2 cups frozen peas, thawed
• 1 cup thinly sliced fresh mushrooms
• 1 cup cubed fully cooked ham
• 1-3/4 cups heavy whipping cream
• 1/4 teaspoon coarsely ground pepper
• 3/4 cup grated Parmesan cheese
• Shredded Parmesan cheese, optional