Pre-heat oven to 350F. Line a cupcake pan with paper liners, or grease it well.
Place chickpea brine in a small saucepan, bring to a boil over medium heat, and let mixture simmer for about 10 minutes, until it has reduced. This step will make so your chickpea brine is more concentrated and make for a more stable frosting. Most recipes don’t call for this step, and you can skip it if you want to. In that case, instead of using 240 ml (1 cup) of chickpea brine, use 120 ml (1/2 cup).
Start whipping the aquafaba (chickpea brine) with a mixer, medium speed.
Sprinkle graham cracker crumbs on top of it. Make sure to sprinkle the graham cracker crumbs on top of the frosting as soon as you pipe the frosting, so it doesn't have a chance to set, and then, the crumbs might not stick.
You can make your own graham crackers to use in this recipe. Here is my recipe for vegan Graham Crackers. But you can find vegan graham crackers at the store, I believe Nabisco's graham crackers are vegan.
Just grind up the graham crackers, and make sure to sprinkle them on top of the cupcakes as the frosting has just been piped, this way the crumbs will stick to the frosting before it sets.