Start by preparing the balsamic roasted peppers, linked above. These can be made a few days in advance to save time.
Season the chicken breast with a drizzle of olive oil, Italian seasoning, salt and pepper.
Heat a grill pan on medium heat and add in a drizzle of olive oil. Cook the chicken for about 6-7 minutes per side, depending on the thickness of the breast. The internal temperature should reach 165 F. Let the chicken rest on a plate before slicing.
While the chicken grills, prepare the pistachio pesto by adding the pesto ingredients to a food processor or blender and blending until smooth.
Once all components are ready, toast your choice of bread. Spread a layer of pesto, followed by sliced avocado, arugula, tomatoes topped with flakey salt, sliced chicken and roasted peppers.