These are such a great summertime treat, and I love using the delicious, in-season berries!
•Graham crackers of choice
You need about 1 frozen banana per sandwich (a sandwich being full sized graham crackers, so the ones shown here are a half sandwich each).
For 4 sandwiches, blend 4 frozen bananas in a high-speed blender or food processor until smooth. Mash about a cup of mixed berries and mix those in. If the mixture is still frozen enough to scoop onto the graham crackers, do that next. Otherwise, spread in a pan and put into the freezer until it freezes up again. Spread some on each graham cracker and top with another graham cracker. Wrap in plastic wrap and freeze for 24 hours (or longer). The graham cracker will soften during that time.