Place the chicken thighs in a bowl and pour the buttermilk over them. Turn to coat and let them sit for at least 15 minutes while you prepare the rest of the ingredients.

In a separate shallow dish, stir together the flour, paprika, garlic powder, 1/2 teaspoon salt, and 1/4 teaspoon black pepper.

Remove each chicken thigh from the buttermilk and let excess drip off. Dredge it in the flour mixture, pressing lightly so the coating sticks well on all sides.

In a large bowl, toss the halved Brussels sprouts with the olive oil, 1/4 teaspoon salt, and 1/4 teaspoon black pepper until evenly coated.

Arrange the coated chicken thighs in a single layer in the air fryer basket. Cook at 375°F for 12 minutes, then flip and cook for another 8 minutes until the coating is golden and the internal temperature reaches 165°F.

Move the cooked chicken to a plate and add the Brussels sprouts to the basket in a single layer. Cook at 380°F for 12 to 15 minutes, shaking the basket halfway through, until the sprouts are tender and edges are browned.

Serve the chicken and Brussels sprouts together while hot.