Trim stems off Brussels sprouts and halve vertically (quarter if larger than a ping-pong ball). Halve any large butternut squash pieces to roughly match smaller pieces. Cut mushrooms into ¼" slices. Peel and mince shallot. Pat chicken breasts dry, and season both sides with a pinch of salt and pepper.

Place butternut squash and Brussels sprouts on prepared baking sheet and toss with 1 tsp. olive oil, garlic salt, and a pinch of pepper. Massage oil and seasoning into vegetables. Spread into a single layer and roast in hot oven, 8-10 minutes. While vegetables roast, sear chicken.

Heat 1 tsp. olive oil in a medium non-stick pan over medium heat. Add chicken to hot pan. Cook undisturbed until browned on one side, 2-3 minutes. After 12 minutes, carefully remove baking sheet from oven and push vegetables to one side. Baking sheet will be hot! Use a utensil. Transfer chicken, seared side up, to empty space. Reserve pan; no need to wipe clean. Roast in hot oven until butternut squash is fork-tender, Brussels sprouts edges begin to brown, and chicken reaches a minimum internal temperature of 165 degrees, 12-14 minutes. While chicken and vegetables roast, make sauce.

Return pan used to sear chicken to medium-high heat and add 2 tsp. olive oil. Add shallot to hot pan and stir constantly until edges are golden-brown and tender, 30-60 seconds. Add mushrooms and stir occasionally until browned, 4-6 minutes. Stir in Italian seasoning, ¼ tsp. salt, and a pinch of pepper.

Stir cream sauce base and 2 Tbsp. water into hot pan until combined. Bring to a low simmer. A low simmer should be a few gentle bubbles. Once simmering, cook until thickened, 2-3 minutes. Remove from burner. If sauce is too thick, add water, 1 Tbsp. at a time, until desired consistency is reached, up to 2 Tbsp. Plate dish as pictured on front of card, topping chicken with sauce. Bon appétit!