Peas, tuna, and noodles in creamy cheese sauce

vegetable oil spray;

2 tablespoons butter;

1 small onion, finely chopped (about 1 cup);

1 cup regular or reducedfat sour cream;

3⁄4 cup whole or 2 percent milk;

11⁄2 cups grated Asiago or Italian blend cheese;

1 teaspoon kosher salt, plus more to taste;

1⁄2 teaspoon ground black pepper, plus more to taste;

2 cups freshly shelled garden peas;

8 ounces wide egg noodles;

2 (6-ounce) cans albacore tuna, drained;

3 tablespoons chopped pimento, drained;

1 cup fresh bread crumbs;

1⁄4 cup coarsely grated Parmesan cheese;

1 tablespoon extravirgin olive oil.

Preheat the oven to 400 F. Mist a 21⁄2-quart baking dish with the spray.
Melt the butter in a large saucepan over medium heat. Add the onion and a pinch of salt and stir to coat. Cover and cook, stirring often, until softened, about 5 minutes. Stir in the sour cream, milk, cheese, salt, and pepper and cook, stirring, until the cheese melts and the sauce is smooth. Remove from the heat.
Fill a large bowl with ice water. Bring a large pot of water to a boil. Add 1⁄2 teaspoon kosher salt per cup of water. Add the peas and cook until barely tender, 3 to 8 minutes, depending on the size and freshness of the peas. Use a slotted spoon or strainer to transfer the peas into the ice water to stop the cooking and set the bright green color. Drain well.
Add the noodles to the boiling water and cook according to package directions, but stop 2 minutes short of the suggested cooking time. Drain well in a colander and stir into the cheese sauce. Stir in the peas, tuna, and pimento. Season with additional salt and pepper. Scrape the mixture into the prepared baking dish.
Stir together the bread crumbs and Parmesan in a small bowl. Drizzle with the oil and toss to coat. Scatter the crumb mixture evenly over the noodle mixture. Bake until the topping is browned, about 20 minutes. Let sit for 5 minutes before serving hot.