Wash and dry all produce. Bring 3/4 cup water to a boil in a small pot. Halve zucchini lengthwise, then slice into thin half-moons. Trim, then thinly slice mushrooms. Finely chop parsley. Halve, peel, and mince shallot. Set aside 2 TBSP flour for sauce, then place the rest in a shallow dish.

Once water is boiling, add rice to pot. Cover, reduce to a simmer, and cook until tender, 15-20 minutes. Heat a drizzle of oil in a large pan over high heat. Add zucchini and cook, tossing, until nicely browned, 7-10 minutes. Season with salt and pepper. Remove pan from heat.

With your hand on one chicken breast, cut 3/4 of the way through center, parallel to cutting board, stopping before you slice through. Open it up, cover with plastic wrap, and pound with a heavy pan or mallet until 1/2 inch thick. Repeat with remaining chicken breast. Season both with salt and pepper, then toss in flour in dish to coat, shaking off excess.

Heat a drizzle of oil in another large pan over medium-high heat. Add chicken and cook until browned and no longer pink in center, 2-3 minutes per side. Remove from pan and set aside to rest. (TIP: Cover chicken with foil to keep warm.) ) Meanwhile, cook rice in microwave according to package instructions.

Melt 1 TBSP butter in pan used to cook chicken over medium-high heat. Add mushrooms and cook, tossing, until tender, 4-5 minutes. Add shallot and another 1 TBSP butter and cook, tossing, until butter melts, 1-2 minutes. Add reserved 2 TBSP flour and stir for 1 minute. Whisk in stock concentrate and 1/2 cup water and let sauce thicken, 1-2 minutes more.

Reduce heat under pan to low. Stir in sour cream and half the parsley. Season with salt and pepper. If zucchini has cooled, quickly reheat in pan. Divide rice, zucchini, and chicken between plates. Drizzle sauce over everything, garnish with remaining parsley, and serve.