Salmon Mac and Cheese

Name: Salmon Mac and Cheese
Ingredients: 1 (16 ounce) package elbow macaroni; 0.25 cup butter, softened; 1 tablespoon olive oil; 1 small onion, minced; 1 (6 ounce) can salmon, drained and flaked; 1 tablespoon seafood seasoning (such as Old Bay®); 1 tablespoon red wine vinegar; 2.5 cups shredded Cheddar cheese; 2 eggs, beaten; 2 cups milk; 0.5 cup vegetable stock; 1 (14.5 ounce) can peas and carrots, drained; 1 (8 ounce) can whole kernel corn, drained; salt and pepper to taste; 3 slices day-old bread; 3 tablespoons grated Parmesan cheese