1 bunch fresh tarragon sprigs, leaves only
1/2 cup plain Greek-style yogurt
1/4 cup harissa sauce (see footnote for recipe link)
2 garlic cloves, peeled
2 tablespoons vinegar or citrus juice
1 tablespoon ground cumin
2 teaspoons kosher salt
4 large chicken breast halves
1/4 cup harissa sauce, for garnish
4 sprigs tarragon, for garnish
Combine tarragon, Greek yogurt, harissa sauce, garlic, vinegar, cumin, and salt in a blender. Puree until smooth, scraping down sides as needed. Pour marinade over chicken breasts in a shallow dish, thoroughly coating both sides. Cover and refrigerate for 2 to 3 hours.
Preheat an outdoor grill for medium-high heat and lightly oil the grate.
Remove chicken breasts from the marinade and place on the pre-heated grill. Cook over medium-high heat until dark grill marks appear, about 7 minutes per side.
Garnish with harissa sauce and a sprig of tarragon.