Heat a large skillet over medium heat and add olive oil. Saute onion and garlic until tender, about 3 minutes.
Add the chicken broth (or water) and soup and whisk until combined. Stir in the egg noodles and frozen vegetables. Season with salt and pepper to taste. Bring mixture to a small boil and then reduce heat. Simmer, stirring occasionally until the noodles are tender and the sauce has reduced, about 20 minutes.
Flake the tuna with a fork and gently fold into the pasta. Top the pasta with the cheese and simmer, covered until cheese melts and tuna is heated through.
Sprinkle the top of the casserole with the crushed croutons and serve. Enjoy!