Wash and dry all produce. Halve potatoes, then place in a medium pot with a large pinch of salt and enough water to cover by 1 inch. Bring to a boil, then lower heat and reduce to a simmer. Cook until just tender, about 6 minutes. Drain.

Meanwhile, peel, halve, and finely chop shallot until you have 1 TBSP. Chop tarragon and parsley until you have 1 TBSP of each. Halve zucchini lengthwise, then slice crosswise into 11/2-inch-long pieces. Using the back of a chef’s knife, smash garlic, then cut each clove in half. Halve lemon, then squeeze 1 TBSP juice into a small bowl.

Heat 1 TBSP olive oil in a large pan over medium-high heat. Season chicken all over with salt and a pinch of white pepper (we sent more). Add to pan and sear until browned, 4 minutes per side.

Heat 1 TBSP olive oil in another large pan over medium heat. Add potatoes, cut-side down, along with garlic. Increase heat to medium-high and cook until potatoes start to brown, about 2 minutes. Add zucchini and cook, tossing, until lightly browned and tender, about 6 minutes. Season with salt and pepper. Remove pan from heat and stir in half the tarragon and parsley.

Stir shallot, stock concentrate, reserved lemon juice, and 1/2 cup water into pan with chicken. Let cook until chicken is no longer pink in center, 4-5 minutes longer. Transfer chicken to a plate, keeping sauce in pan. Whisk 1 tsp mustard into pan (we sent more), then bring mixture to a boil. Reduce heat to medium and let simmer until reduced to a saucy consistency, 2-3 minutes.

Once sauce has reduced, stir in remaining tarragon and parsley. Remove pan from heat. Stir in sour cream. Divide veggies and chicken between plates. Spoon sauce over chicken and serve.