To make the pistachio pesto, combine all the ingredients into a food processor. Blend together until combined. Taste and adjust salt to personal preference. Store in the refrigerator in an air tight container up to 4 days until ready to eat with the sandwiches.
To make the breakfast sandwiches, preheat the oven to 350 degrees F. Heat 1 tablespoon oil in a medium skillet. Add the diced onion and bell pepper. Sauté the onion and bell pepper for about 5 minutes on medium heat or until the vegetables are tender. Add the minced garlic clove and sauté for an additional minute. Turn off heat and add spinach.
Grease a 11x9 (or similar) baking pan. Add the cooked vegetables and spread out evenly.
Add the eggs, salt, pepper and cottage cheese to a blender. Blend together until smooth. Pour the egg mixture over the vegetables. Gently stir together.
Bake the eggs for 20-25 minutes or until fully set. Remove from the oven and the eggs cool. Cut the eggs into 6 equal squares.
To build the breakfast sandwiches, open the English muffins and add a egg square. Top with sliced gouda cheese. Top with the English muffin.
Wrap each sandwich tightly in foil. Place either in the fridge if eating within 2-3 days or the freezer to enjoy within 3 months. Reheat each breakfast sandwich in the microwave wrapped in a paper towel when ready to enjoy. After heated through, add a generous layer of pistachio pesto.