Even your most staunchly anti-broccoli family member will ask for seconds when the veggies are tossed with cauliflower, crisp bacon, shallot, and sherry vinegar.
Set a steamer basket in a saucepan with 2 inches simmering water. Add cauliflower, cover, and steam until tender, 10 minutes. Transfer to a serving dish. Repeat with broccoli.
Meanwhile, in a large skillet, cook bacon over medium-high until crisp, about 8 minutes, flipping once. With tongs, transfer bacon to paper towels to drain. Reduce heat to medium, add shallot, and cook until translucent, about 3 minutes. Carefully whisk in sherry vinegar and season with salt and pepper. Immediately pour over vegetables. Crumble bacon and add to vegetables; toss to combine.