Rub the chicken breasts with fajita seasoning and let marinate for 30 minutes.

In a skillet over medium heat, cook the chicken on both sides until it reaches an internal temperature of 165°F. Remove the chicken from the skillet and set aside.

Add the onion and bell pepper to the same hot skillet. Cook over high heat, stirring occasionally, until softened. Remove the vegetables from the skillet and set aside.

Brown the potatoes or frozen hash browns in vegetable oil until crisp. Season with salt and pepper to taste. Divide the hash browns in half and place on serving platters.

Whisk the eggs with the half and half and season with salt and pepper to taste. Use the egg mixture to make two omelets. Place one omelet on top of each plate of hash browns.

Slice the reserved chicken breast and place half of the chicken, onions, and peppers over each omelet. Sprinkle half of the shredded cheddar over each plate. Serve with sour cream, guacamole, and salsa if desired.