In a medium bowl, whisk together honey, whole grain mustard, extra virgin olive oil, fresh lemon juice, chopped cilantro, minced garlic, yellow curry powder, kosher salt, freshly cracked black pepper, and crushed red pepper flakes. Blend until smooth and set aside 1/4 cup for salad.

Coat the boneless skinless chicken thighs with the marinade, cover, and refrigerate for at least 30 minutes, or up to 4 hours.

In a large bowl, combine sliced cucumbers, diced peaches, chopped cilantro, and torn mint leaves. Drizzle with reserved marinade and a squeeze of lemon juice. Toss gently and let sit for 10 minutes.

Preheat your grill to medium-low (about 350°F). Place the marinated chicken on the grill and cook for approximately 4 minutes per side, brushing with the reserved marinade during the last minute.

Remove the chicken from the grill, let it rest for a few minutes, and serve topped with the peach salad.