Tuna Cazuela

I grew up hating Tuna Helper as a child, making me weary of tuna casseroles as an adult, but this dish is surprisingly lovely! It is a recipe from Food and Wine. We've had it twice now, and both times, we have really enjoyed it.  

Ingredients

12 oz farfalle pasta
4 tbsp butter
1 med onion, chopped
2 tbsp flour
3c whole milk or half & half
1 1/2c frozen peas
1/2 cup shredded parmesan (or TJ's Quatro Formaggio)
1 can white tuna - 6oz
Salt
Freshly ground pepper
1/2c panko bread crumbs

1. Preheat oven to 450°. Cook pasta in large pot of boiling water until al dente. Drain when done.
2. While pasta is cooking, melt 3 tablespoons butter in a large saucepan. Add chopped onion and cook over high heat, until softened, ~3 minutes. Add the flour and cook while stirring for 1 minute. Add milk and bring to boil, then lower heat and continue to cook sauce over medium heat, stirring occasionally, until thickened, about 3 minutes.
3. Add the pasta, frozen peas, cheese and tuna. Season with salt and pepper. Transfer the mixture to a large baking dish (a cazuela or casserole dish).
4. In a skillet, melt 1 tablespoon butter. Add panko bread crumbs and stir while cooking over medium heat, until golden, or about 1 minute. Sprinkle evenly over casserole and bake for 10 minutes, or until bubbling. Serve right away with a nice salad.