Step 1

Preheat the oven to 350 F.

Step 2

Bring a large pot of water to boil and cook the noodles according to package instructions, then drain and set aside.

Step 3

While the noodles are cooking, add the butter to a large, heavy-bottomed pan or cast-iron over. Once butter is melted, add the onion, garlic, and mushrooms. Saute for 4-5 minutes, until the onion and mushrooms have started to brown.

Step 4

Add the flour to the onion and mushroom mixture and toss to coat, then slowly whisk in the milk and broth. Continue whisking until there are no remaining clumps.

Step 5

Next, stir in the salt, pepper, peas, and tuna and let the mixture come to a bubble. Once bubbling, add the cooked and drained pasta and toss to coat.

Step 6

Transfer the mixture to a 3 quart casserole dish, top with cheese, if desired, and bake at 350 for 20 minutes, until hot and bubbling. Remove from the oven, garnish with parsley, and serve!