1) In a bowl, mix together cheese, mayonnaise, milk, and bacon until spreadable.
2) Smear the cheese mixture on 4 toasts.
3) Place avocado slices over the cheese spread.
4) Cover the avocado with the remaining toasts.
5) Cut the Avocado Bleu Cheese Sandwich diagonally into half.
6) Serve with a small mixed salad if desired.