Pat dry and cube the chicken breasts into bite-sized pieces. Season generously with garlic powder, onion powder, smoked paprika, salt, and black pepper.

Heat olive oil in a large skillet over medium-high heat. Add chicken cubes and sear for 5-7 minutes until golden brown. Remove from skillet and set aside.

In the same skillet, reduce heat to medium and sauté chopped onion for 2-3 minutes until softened. Stir in garlic powder and cook for an additional minute. Add long-grain white rice and sauté for 1 minute.

Pour in chicken broth, increase heat to high, and bring to a boil. Cover and simmer for 15 minutes, then remove from heat.

In a separate saucepan, melt unsalted butter over medium heat. Stir in all-purpose flour, whisking constantly for 2-3 minutes to create a roux. Gradually whisk in whole milk and chicken broth until thickened, about 5-7 minutes.

Season sauce with thyme, salt, and pepper. Return cooked chicken cubes to the sauce, mixing gently to coat. Simmer on low heat for 5 minutes.

Serve over fluffy rice and garnish with parsley or chives.