Preheat and Prep: Preheat your oven to 375°F (190°C). Grease a 9x13 inch casserole dish. Make sure your chicken breast is already cooked and shredded. If using cottage cheese, blend it in a small blender until perfectly smooth, setting it aside.

Sauté the Aromatics: In a large Dutch oven or deep skillet, melt the butter or heat the olive oil over medium heat. Add the diced onion, chopped carrots, and celery. Cook, stirring occasionally, until the vegetables begin to soften, about 5 to 7 minutes. You want them tender, but not mushy.

Add the Garlic and Herbs: Stir in the minced garlic, thyme, and rosemary. Cook for about 1 minute until fragrant. This part is crucial, the smell right here is pure comfort. Do not let the garlic burn, or it will turn bitter.

Build the Roux (Thickening Agent): Sprinkle the flour over the vegetables and stir continuously for 1 to 2 minutes. The flour will absorb the fat, creating a slight paste—this is your simple roux foundation, which provides incredible body to the sauce.

Deglaze and Simmer: Slowly whisk in the chicken broth, ensuring there are no lumps. Next, pour in the milk or half and half. Bring the mixture to a gentle boil, then reduce the heat immediately to a simmer. Allow the sauce to thicken slightly, usually about 3 to 5 minutes. It should coat the back of a spoon.

Fold in the Fillings and Protein: Remove the skillet from the heat. Stir in the shredded chicken breast (or rotisserie chicken), the frozen peas and corn, and any optional add-ins like spinach or sweet potatoes. Now, stir in your secret protein boost: the smooth Greek yogurt or blended cottage cheese. Taste the filling and adjust seasoning with salt and pepper. Remember, this must taste perfectly seasoned now, as the flavors won't intensify much in the oven.

Bake the Pot Pie: Pour the entire creamy, vegetable-studded mixture into your prepared casserole dish. You can smooth the top with a spatula. Place the dish in the preheated oven.

The Finish: Bake for 20 to 25 minutes. The edges of the filling should be bubbling beautifully, and the top will be lightly golden brown. The goal is to heat everything through and let the flavors meld perfectly.

Rest and Serve: Let the High Protein Crustless Chicken Pot Pie rest on the counter for 5 to 10 minutes before serving. This resting time is vital; it allows the sauce to set up completely, ensuring a thick, hearty serving. Scoop generous amounts onto plates and watch the family gather around, drawn in by the pure aroma of traditional pot pie comfort.