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.
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.
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.
A trick for getting those pro-looking crosshatch marks on chicken and vegetables: Imagine your 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 from grill and spoon 1 Tbsp. vinaigrette (reserve remaining for garnish) over each chicken breast. Tent with foil and rest at least 5 minutes.
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!