In a small saucepan over medium heat, melt the unsalted butter until bubbly, add minced garlic and sauté until fragrant, about 1-2 minutes. Remove from heat and stir in lemon juice, Dijon mustard, smoked paprika, red pepper flakes, parsley, salt, and black pepper.

Cut the chicken thighs into bite-sized pieces and place them in a mixing bowl. Pour about two-thirds of the cowboy butter over the chicken and toss to coat. Cover with plastic wrap and marinate in the refrigerator for at least 30 minutes or up to 2 hours.

Preheat your grill to medium-high heat, around 400°F (200°C). Thread the marinated chicken pieces onto skewers.

Place the chicken skewers on the preheated grill and cook for 10-12 minutes, turning occasionally, until cooked through.

Brush the remaining cowboy butter over the skewers, garnish with lemon juice and parsley, and serve hot.