2 pounds baby red potatoes, sliced in half (they should all be about the same size so they cook evenly)
6 tablespoons unsalted butter, cut into tablespoons
1/2 cup grated Parmigiano-Reggiano
3/4 teaspoon salt
1/2 teaspoon ground black pepper
1 teaspoon fresh chives, finely chopped (optional)
Bring large pot of salted water to a boil. Cook potatoes until fork-tender, about 15 minutes.
Use a slotted spoon or hand-held strainer to transfer cooked potatoes to a shallow bowl or serving dish. Reserve hot cooking water. Top potatoes with butter, Parmigiano Reggiano, salt and pepper. Use a fork to smash the potatoes, adding cooking liquid as necessary to make potatoes as creamy as you like (I usually add about a ½ cup total). Taste and adjust seasoning if necessary. Sprinkle fresh chives over top and serve.