Preheat oven to 400º F.
Bring water to boil in a 4 quart pot and add 2 tablespoons salt. Place potatoes in pot and cover with water. Boil potatoes until tender (approximately 15 minutes). Drain and let them sit until potatoes are cool enough to handle. Transfer potatoes to a baking sheet.
In a small microwavable bowl, place Kerrygold Salted Butter, garlic, rosemary, salt and pepper. Melt together and mix until combined and pour over potatoes.
Using the bottom of a glass or mug, smash potatoes into flat patties. Bake until golden brown and crisp (about 20 minutes).
Shred 1 cup Kerrygold Reserve Cheddar and 1 cup Kerrygold Dubliner Cheese and combine in a mixing bowl. Generously top potatoes with shredded Kerrygold cheese mixture and bake until melted.
Garnish with crumbled bacon, chives, cilantro, and sour cream before serving.