Often times, a sauce is something creamy and rich or boiled and reduced until it's not much more than a sticky glaze. Sauces are complicated and complex; not for nothing do the French have five “mother sauces.” In this meal, we've got different adjectives from the sauce lexicon: simple, easy, and light. This mustard vinaigrette is springy and alive, the perfect accompaniment to the grilled chicken. Ditch the rich and cancel the creamy; the vinaigrette is here to stay.
Trim woody ends off asparagus.
Trim zucchini ends and cut into ¼" slices on an angle.
Pat chicken breasts dry, and season both sides with ¼ tsp. salt and a pinch of pepper.
Make the Vinaigrette
Heat a grill or grill pan to medium heat. When using an outdoor grill with enough room, feel free to cook all elements at once.
While grill heats, combine vinegar, mustard, and sugar in a mixing bowl. Slowly drizzle in 2 Tbsp. olive oil while whisking constantly. Season with a pinch of salt and pepper. Set aside.
Grill the Chicken
Drizzle 1 tsp. olive oil over chicken breasts. Place chicken on hot grill and cook until browned and chicken reaches the minimum internal temperature of 165 degrees, 4-6 minutes per side.
How to get pro-looking crosshatch marks: Imagine the grill is a clock and place meat on grill so tip points at 10 o'clock. After 2-3 minutes, rotate so tip points at 2, and cook another 2-3 minutes. Repeat on second side.
Remove chicken to a plate and spoon 1 Tbsp. vinaigrette (reserve remaining for garnish) over each chicken breast. Tent with foil and rest at least 5 minutes. Keep grill over medium heat.
Grill the Vegetables
Drizzle 1 tsp. olive oil over asparagus and zucchini. Season with ¼ tsp. salt and a pinch of pepper.
Working in batches if necessary, place zucchini and asparagus on hot grill. Flip occasionally until lightly charred and tender, 2-4 minutes.
Remove from grill.
Finish the Dish
Plate dish as pictured on front of card, garnishing chicken with remaining vinaigrette and vegetables with feta. Bon appétit!