In a medium mixing bowl, combine the drained and rinsed beans, 1 tablespoon of the olive oil, and the juice of a half lemon.
Roughly mash with a potato masher or a fork, leaving it a little chunky. It should be a good consistency for spreading on a sandwich. Add additional olive oil, up to 1 more tablespoon if the mixture is too thick. Add salt and pepper to taste.
Refrigerate until ready to use. Can make as far as one or two days ahead. This sandwich filling can also be used as a vegetable or chip dip. Stir before using.
To assemble the sandwiches:
Line up to eight slices of whole grain or multigrain bread with lettuce on four and arugula or sprouts on the other four slices.
If using yellow mustard (optional), add it on top of the lettuce. Then top with 1/4 of the white bean sandwich filling. If not using mustard, just add the filling on top of each slice of bread with lettuce.
Arrange the avocados, cucumber slices and red onion slices. Season with salt and pepper, then fold the two halves of the sandwich together. Cut in half before serving. Serve immediately or wrap and refrigerate.
These would also taste great with a slice of your favorite vegan cheese. You can also use Everything Bagel seasoning in place of salt and pepper to season the sandwich.