Prepare the pistachio pesto by adding all of the ingredients to a food processor or blender and blending until smooth. Adjust salt to taste and set aside.
Crack the eggs into a bowl and whisk together with the herbs and pinch of salt and peppe.
Heat a non-stick skillet on medium/low heat with a little cooking spray, and pour the eggs in. Let cook for about 3 minutes, then gently fold the edges of the eggs into the center. Cook the eggs for about 7 minutes total until cooked though, folding them in every couple of minutes to create the omelette.
While the eggs cook, toast your bread. Place the bread onto a sheet pan and drizzle with olive oil, then place the fresh mozzarella slices onto one side of the bread. Set under the broiler for about 2-3 minutes to melt.
Assemble your sandwich with the pesto, omelette, sliced tomatoes, avocado and arugula with a pinch of salt & pepper
Leftover pesto can be refrigerated for up to 1 week, or frozen for up to 2 months.