Using a sharp mandoline or a food processor equipped with a slicing blade (my preference), shred the brussels sprouts, endives, and shallot. If using the mandoline, use the stem of the Brussels sprout and endive to shred and if using the food processor, slice the end off. Place the mixture in a large bowl and break up any large pieces of Brussels sprouts.
Cut the peel from the outside of the grapefruit and orange. Separate into sections and remove the membrane from the outside of each slice and cut any large citrus chunks into smaller pieces. Add the fruit to the shredded endive mixture along with the almonds and cheese.
In small jar with lid, shake together the olive oil, lemon juice, honey, and salt. Pour 1/2 the mixture over the salad and toss until everything is well combined and salad is dressed. Add more of the dressing if needed (this will all depend on how juicy the citrus was to begin with.) Serve immediately or let sit for an hour allow brussels sprouts to soften.
Notes
*If you choose to not serve the salad right away, the texture will be more akin to a slaw. I recommend tossing with some cooked grains or you could even add a bit of lettuce or arugula to the mix!