Tuna Noodle Casserole with Mushrooms Recipe

Ingredients

• 3.25 cups penne pasta
• 1 tablespoon butter, or more to taste
• 1.5 cups sliced fresh mushrooms
• 1 onion, finely chopped
• 1 tablespoon all-purpose flour
• 1.25 cups milk
• 0.5 cup frozen peas
• 0.5 cup frozen sweet corn
• 1 (7 ounce) can tuna, drained
• 0.5 (8 ounce) package shredded Cheddar cheese