Remove the stems from portobello mushrooms, using kitchen towel to wipe any dirt from it, set aside.
Remove pit from the avocado, thinly sliced.
Heat the skillet, add the oil and portobello mushrooms, sauté for 2 minutes over medium heat. Flip the portobello mushroom.
Mix the Swanson No Added msg Concentrated Chicken Stock with water, add on the skillet. Cover with a lid and simmer until the portobello mushroom cooked through. Add pepper to taste.
Grill the burger buns in a pan until hot. Take out.
In a bowl, beat the eggs. Heat the skillet with oil in high heat, pour the egg. Scramble until no visible liquid egg remains.
Assemble the avocado, portobello mushroom and the scramble egg on the burger bun. Serve hot.