Preheat oven to 400°F (205°C).
Wash potatoes thoroughly and pat dry. Slice in half lengthwise.
Place the potatoes in a medium heavy-bottomed pot and cover with cold water. Salt the water and add the smashed garlic cloves to infuse the potatoes with flavor.
Bring to a boil over medium-high heat and then reduce to a simmer. Continue cooking the potatoes until they are fork-tender, approximately 20-22 minutes.
Drain the potatoes and season them with 2 tablespoons of rice vinegar, a pinch of salt, and pepper.
Set a pot of salted water on the stove and bring to a boil; get a large bowl of ice water ready, too.
Cut the bottoms off of the Brussels sprouts to make it easier to peel the petals off. Once the water has come to a rolling boil, add the Brussels sprout petals and cook for 30 seconds to a minute until they turn vibrant green.
Immediately strain out the petals and put them into the ice water to stop the cooking process.
Lay 3-4 slices of deli corned beef on a lined baking sheet and drizzle with a little bit of oil. Bake for 12-15 minutes, or until crispy.
Remove from oven and let cool slightly. Crumble or chop the baked slices into bite-sized pieces.
Chop green onions and parsley.
To make the vinaigrette, whisk together all of the ingredients in a bowl. Adjust the amount of horseradish to your liking if you want it more or less punchy!
Place the boiled potatoes, Brussels petals, green onions, and parsley in a large bowl. Pour the vinaigrette over top and toss gently to combine.
To plate, top the dressed vegetable mixture with the crispy corned beef crumbles, crushed potato chips, and cracked black pepper.