When preparing Brussels sprouts, the combination of butter and sherry vinegar is so beautiful, simple, and straightforward, it really lets your sprouts shine. This is a great side dish for any occasion.
Prepare each Brussels sprout by gently working a small knife around the core and pulling it out. Repeat with all your sprouts, then remove the individual leaves. The tight knot of inner leaves can be left intact and sliced thinly. Meanwhile, prepare for blanching by bringing 2 quarts of water to a boil over high heat; make an ice bath with a bowl and strainer. Season the boiling water with ¾ teaspoon salt.
Add the Brussels sprouts leaves to rapidly boiling water. Blanch for 1 minute, then remove to the ice bath. Drain the leaves and place onto a cloth towel; roll up the towel and gently apply pressure to remove as much water as possible.
Heat the olive oil in a 12-inch sauté pan over medium-high heat until it is almost smoking; then add the leaves, being careful not to crowd the pan. (Cook in batches, if necessary.) Let the leaves cook undisturbed for 30 seconds; then flip the leaves, add the butter and half the salt, and sauté until the leaves have some golden coloring and crisp edges, 1 more minute. Add the sherry vinegar and season with the remaining salt. Serve immediately.