In a large skillet over medium heat, add the ground chicken, onion, garlic, and bell pepper. Cook until the chicken is browned and the vegetables are softened, about 5-7 minutes.

Stir in the Cajun seasoning, diced tomatoes, Worcestershire sauce, salt, and pepper. Simmer for about 10 minutes until heated through and slightly thickened.

While the chicken mixture is simmering, prepare the cheese sauce. In a small saucepan over low heat, melt the butter, then whisk in the milk. Gradually add the cheddar cheese, stirring until melted and smooth.

Toast the brioche buns until golden.

To assemble, spoon the Cajun chicken mixture onto the bottom half of each bun, drizzle with cheddar cheese sauce, and top with the other half of the bun. Serve immediately.