Grilled Chicken Tacos

ALL YOU NEED :

1 medium onion, cut into wedges

2 garlic cloves, finely chopped

1 pound skinless, boneless chicken thighs

1 tablespoon cumin seeds, coarsely crushed

1 tablespoon vegetable oil

1 teaspoon kosher salt

1/2 teaspoon freshly ground black pepper

8 corn tortillas, warmed (for serving)

2 avocados, sliced (for serving)

Charred Tomatillo Salsa Verde

Cilantro sprigs, sliced radishes, and lime wedges (for serving)

1 cup sour cream

2 tablespoons milk