In a large bowl, combine the chicken and mayonnaise. Season to taste with salt and pepper. Chill the chicken salad until ready to serve.
Cook the bacon until crisp. Drain on paper toweling.
Assemble the sandwiches by spreading mayonnaise thinly over the first slice of bread. Top with tomatoes, bacon, and some baby greens. Add a second slice of bread.
Divide the chicken salad over this second slice of bread. Top with more baby greens and the third slice of bread. Serve immediately.
If packing for take-away, wrap each sandwich carefully and consume within 8 hours. Toasting and cooling the bread before assembly will help it hold up longer.
Shop at Costco. When I didmy big grocery store showdown, I learned that Costco has the best price for a lot of the things I buy, plus they sell all the ingredients needed for this recipe. I love their rotisserie chickens and buy their uncured bacon in bulk from them. They also have good prices on whole grain bread.