Preheat the oven to 375 degrees. Grease an 8-inch-square baking pan.
Place the walnuts in a dry skillet and toast over medium heat until light brown and fragrant, 3 to 4 minutes, shaking often. Transfer them to a food processor.
Add the oats, dried fruit, chocolate chips, maple syrup, peanut butter, vegan butter and vanilla to the food processor, and pulse until crumbly. Continue to process until the mixture is well combined. Add a little water, a tablespoon at a time, if the mixture is too crumbly to stick together. Press the mixture evenly into the prepared pan.
Bake until lightly browned, about 20 minutes. Remove from the oven and set aside to cool, then refrigerate until completely cold. Cut into 2- by 4-inch bars. Wrap each bar individually in plastic wrap for easy transport.