Step 1
Place a rack in center of oven; preheat to 400°. Prepare dinner 12 oz. extensive egg noodles in massive pot of boiling salted water, stirring sometimes, till very al dente, about 2 minutes. Drain noodles; reserve pot.
Step 2
Take away darkish inexperienced components from 1 bunch scallions and thinly slice; put aside. Thinly slice white and pale inexperienced components.
Step 3
Soften 4 Tbsp. unsalted butter in reserved pot over medium warmth. Prepare dinner white and pale inexperienced components of scallions, 1 massive onion, finely chopped, and 1 head of garlic, cloves separated, coarsely chopped, stirring sometimes, till softened however not browned, 6–8 minutes. Add ¼ cup all-purpose flour and cook dinner, stirring always, till flour is pale golden, about 3 minutes. Pour in 4 cups water, whisking always to dissolve flour, and produce to boil. Prepare dinner, whisking typically, till sauce is barely thickened, about 5 minutes; take away from warmth.
Step 4
Add zest of 1 lemon, 8 oz. cream cheese, reduce into 1″ items, room temperature, 8 oz. Monterey Jack or pepper Jack cheese, coarsely grated, ½ cup yellow or white miso, ¼ cup chili sauce (resembling sriracha), 2 Tbsp. hen bouillon paste, and 1 Tbsp. soy sauce, ideally low-sodium, to sauce; whisk vigorously till included and cheese is absolutely melted.
Step 5
Gently stir noodles, three 5-oz. cans oil-packed tuna, drained, and 1½ cups frozen peas into sauce; style and season with salt if wanted. Switch combination to a 13×9″ baking dish and degree floor. Scatter 4 oz. potato chips, coarsely crushed, over in an excellent layer. Bake casserole till sizzling all through and chips are starting to brown, 15–20 minutes. High with extra lemon zest and reserved darkish inexperienced components of scallions; season with pepper.
