
5 tablespoons unsalted butter, divided
3 cups sliced leeks (white and pale green parts), rinsed
Coarse kosher salt
Ground white pepper
2 cups heavy whipping cream
6 cloves garlic, minced
1½ pounds baby Yukon Gold potatoes, thinly sliced
8 ounces thinly sliced prosciutto, torn into 1- to 2-inch pieces
8 ounces smoked Gouda cheese, shredded