01 -
Preheat the oven to 375 degrees Fahrenheit. Lightly butter a 9x13 inch or 3-quart baking dish to prevent sticking.
02 -
Boil the egg noodles in well-salted water until 1 to 2 minutes less than package instructions. Drain and reserve ½ cup pasta water.
03 -
Melt 2 tablespoons salted butter in a large skillet over medium heat. Cook the diced onion and shallot until translucent and sweet, about 4 to 6 minutes. Add minced garlic and cook for 30 seconds until fragrant, taking care not to brown.
04 -
Sprinkle in 2 tablespoons all-purpose flour and stir continuously for 1 minute to eliminate raw taste and form a paste.
05 -
Gradually whisk in 1 cup chicken broth and 1 cup half-and-half cream, smoothing lumps. Add 2 teaspoons vegetable bouillon powder, ½ teaspoon salt, ¼ teaspoon black pepper, ½ teaspoon dried thyme, and ½ teaspoon Dijon mustard. Simmer for 3 to 5 minutes until the sauce thickly coats a spoon.
06 -
Remove from heat and whisk in ½ cup Greek yogurt until the sauce is silky. To avoid curdling, temper the yogurt with a ladle of hot sauce before combining.
07 -
Gently fold in the drained tuna, frozen green peas, and 1 cup shredded white cheddar cheese until evenly distributed.
08 -
Toss the sauce mixture with the cooked noodles, adding reserved pasta water if the mixture is too stiff.
09 -
Spread the mixture evenly into the prepared baking dish, smoothing the top for uniform browning.
10 -
Combine ½ cup shredded white cheddar cheese with 1 tablespoon melted unsalted butter, tossing until cheese is lightly coated. Evenly scatter over the casserole.
11 -
Bake at 375 degrees Fahrenheit for 20 to 25 minutes until bubbly at the edges and the top is melted with golden spots. For additional color, broil 1 to 2 minutes, monitoring closely.
12 -
Allow the casserole to rest for 10 minutes before slicing to set. Serve warm.