Heat the oil in a non-stick pan over medium heat. Add the eggs and avocado, move the egg around the pan until it is firm and fluffy, no longer runny. Season with salt and pepper and set aside.
Layer the bread with cheese, tomato and eggs.
Melt some of the butter in a non-stick pan, place the sandwich into the pan, cover with a lid and cook on both sides until golden brown and the cheese has melted.
In a non-stick pan over medium heat, brown the chicken sausage.
Cut the sandwich in half and serve with chicken sausage and blackberries.