How to Make It
Preheat oven to 350°F. Spread almonds on a large rimmed baking sheet. Bake in preheated oven until golden, 6 to 7 minutes. Remove from pan, and let cool 10 minutes.
Whisk together buttermilk, mayonnaise, garlic, salt, and pepper in a very large bowl. Add brussels sprouts, arugula, and parsley; toss well to coat. Sprinkle with toasted almonds, and serve.
Quick Pickled Shallots: Combine 1/2 cup red wine vinegar, 1/4 cup water, 2 teaspoons granulated sugar, and 2 teaspoons kosher salt in a jar with a tight-fitting lid. Attach lid, and shake well. Remove lid; add 1/2 cup thinly sliced shallot rings. Attach lid, and shake well. Refrigerate 30 minutes. Drain. Scatter on salad.