(Serves 4 with leftovers)
3 pounds Yukon gold potatoes, peeled and cut into 1/2-inch cubes
5 slices bacon, cut into 1/2-inch pieces
3 tablespoons butter
1⁄2 large leek, diced small using white and light green parts only
2 Tablespoons + 2 teaspoons salt, divided
1 1⁄2 teaspoons freshly ground black pepper, divided
2 cups whole milk
4 green onions, finely sliced
1 cup shredded cheddar cheese
Place potatoes into a large pot, cover with water and add 2 Tablespoons salt; bring to a boil. Cook until fork-tender, about 10 minutes. Do not drain!
Add butter, remaining salt and pepper and coarse mash potatoes, leaving some potato cubes unmashed. Add milk when butter has melted.
Place bacon and leeks in a large saucepan and cook over medium-high heat, turning occasionally, until crispy, about 8 minutes. Drain bacon slices and leeks on paper towels.
Add bacon and leeks to the pot with potatoes and stir to incorporate everything together.
Ladle into serving bowls. Garnish with green onions, and 1⁄4 cup cheddar per bowl.