01 -
Preheat oven to 375°F (190°C). Butter or spray a 9x13 inch baking dish. Bring a large pot of salted water to a boil over medium-high heat. Cook egg noodles until slightly under al dente, about 1 to 2 minutes less than package instructions. Drain, toss with a drizzle of olive oil, and set aside.
02 -
Melt salted butter in a large skillet over medium heat. Add diced onion and shallot; cook until soft and translucent, about 5 minutes, stirring occasionally. Add minced garlic and cook for 30 seconds, ensuring it does not brown.
03 -
Sprinkle flour over the cooked vegetables and stir continuously for 1 to 2 minutes to form a roux. Gradually whisk in chicken broth and half-and-half, breaking up any lumps. Stir in vegetable bouillon powder, salt, black pepper, dried thyme, and Dijon mustard. Simmer, stirring often, until sauce thickens and becomes creamy, about 5 to 7 minutes.
04 -
Remove pan from heat and whisk in Greek yogurt until smooth. Gently fold in drained tuna flakes and frozen peas. Stir in 1 cup shredded white cheddar until evenly incorporated and beginning to melt. Add drained noodles and toss gently to coat thoroughly.
05 -
Transfer noodle mixture evenly into the prepared baking dish. In a small bowl, combine the remaining ½ cup shredded cheddar with melted unsalted butter. Sprinkle this mixture evenly over the casserole surface.
06 -
Bake for 20 to 25 minutes until the topping is golden and bubbling at edges. Remove from oven and allow to rest for 10 minutes to thicken the sauce and enhance slicing.