Make aioli by combining mayo, sundried tomatoes, garlic clove, salt and pepper in a small bowl and whisking until incorporated.
Toast bread if you like. Spread aioli on one piece of bread and a layer of goat cheese on the other piece. Layer either side with 2 slices bacon, a generous handful of arugula, avocado slices/mashed avocado to taste, and a layer of red onion. Close sandwich, slice and enjoy! I don’t recommend making sandwiches more than a few hours in advance.
Leftover aioli will keep tightly sealed up to 4 days in the fridge. To best preserve your remaining avocado throughout the week, sprinkle the flesh side with lemon juice, keep the pit in and wrap tightly with plastic wrap.