Preheat your oven to 375°F and lightly grease a 9x13 inch baking dish. While the oven heats, prepare all your ingredients: dice the onion into small pieces, mince the garlic, cut the broccoli into bite-sized florets, and dice the carrots. Shred the cheddar cheese fresh if you haven't already—I find freshly shredded cheese melts much more smoothly than pre-shredded varieties. This mise en place setup ensures everything moves quickly once you start cooking.

Bring a pot of salted water to a boil and add the egg pasta, cooking it for 2 minutes less than the package directions recommend. This parboiling prevents the pasta from becoming mushy during baking. While the pasta cooks, heat the olive oil in a large skillet over medium-high heat and brown the ground turkey, breaking it apart as it cooks, for about 5-7 minutes until no pink remains. Drain the cooked pasta and toss lightly with a small drizzle of olive oil to prevent sticking, then set aside. Transfer the cooked turkey to a bowl.

In the same skillet, melt the butter over medium heat. Add the diced onions, broccoli, and carrots along with a pinch of salt and pepper, and sauté for 2-3 minutes until they begin to soften. Add the minced garlic and cook for another minute until fragrant. Sprinkle the flour over the vegetables and stir constantly for about 1 minute—this roux will thicken your sauce and give it body. The flour coating the vegetables is what creates a smooth, creamy sauce rather than a thin, watery one.

Slowly pour in the chicken broth and milk while stirring constantly to avoid lumps. Add the Dijon mustard and thyme, stirring to combine. Bring the mixture to a gentle boil, then reduce heat to low and simmer for 5-7 minutes, stirring occasionally, until the sauce thickens enough to coat the back of a spoon. Remove from heat and stir in the freshly shredded cheddar cheese and sour cream until fully melted and smooth. I always add the sour cream after removing from heat because high temperatures can cause it to break and become grainy.

Add the cooked turkey from Step 2 and the cooked pasta from Step 2 to the sauce, stirring gently until everything is evenly coated. Pour this mixture into your prepared baking dish, spreading it into an even layer.

In a small bowl, combine the panko breadcrumbs and grated Parmesan cheese. Drizzle this mixture with about 2 tablespoons of olive oil and toss with a fork until the crumbs are evenly moistened—this helps them brown beautifully. Spread the topping evenly over the casserole. Bake at 375°F for 20-25 minutes until the top is golden brown and the sauce is bubbling around the edges.