Preheat oven to 400°F (200°C).

Pat chicken thighs completely dry and bring to room temperature. Season both sides with 2 teaspoons Lawry's seasoning salt, 1 tablespoon garlic powder, 1 tablespoon paprika, and 1 Sazon packet. Rub mixture thoroughly onto chicken.

In a bowl, combine flour with 1 tablespoon Lawry's seasoning salt, 1 tablespoon garlic powder, 1 tablespoon paprika, and 2 teaspoons cracked black pepper. Whisk until evenly distributed.

Coat each seasoned chicken thigh completely in the prepared flour mixture, shaking off excess. Reserve remaining seasoned flour for gravy.

Heat oil in large oven-safe pan over medium-high heat. Place chicken thighs skin side down and cook undisturbed for 5 minutes per side until deeply golden brown. Remove chicken and set aside.

Remove excess oil from pan, leaving approximately 2 tablespoons. Add butter, sliced onion, chopped garlic, crushed red pepper flakes, cracked black pepper, and 4 tablespoons of the reserved seasoned flour. Whisk constantly and sauté for 3 to 5 minutes to create a light roux.

Gradually whisk in chicken stock, stirring continuously to prevent lumps. Simmer for 3 to 5 minutes until gravy begins to thicken.

Pour in heavy cream and continue whisking until fully incorporated and smooth.

Return seared chicken thighs to the pan along with any accumulated juices, nestling them into the gravy.

Bring contents to a boil on stovetop. Cover pan tightly and transfer to preheated oven. Bake for 45 minutes until chicken is cooked through and gravy has thickened.

Remove from oven and uncover. Spoon gravy generously over each chicken thigh, garnish with dried parsley, and serve immediately with mashed potatoes.