1 1/2 pounds baby red potatoes (about 2 inches in diameter)
3 tablespoons olive oil
1 clove garlic, minced
Salt and freshly ground black pepper
2 tablespoons grated Parmesan cheese
12 to 16 ounces cooked chicken sausages, such as chicken apple, cut into 2-inch pieces
1 tablespoon coarsely chopped fresh parsley (optional)
Heat the oven to 450°F. Meanwhile, boil the potatoes.
Place the potatoes in a medium saucepan, season generously with salt, and add enough water to cover the potatoes by about 1 inch. Bring to a boil over high heat, then reduce the heat to medium-low and simmer uncovered until the potatoes are cooked through, 12 to 15 minutes. Drain the potatoes and set aside to cool slightly. (The potatoes can be boiled and stored in the refrigerator up to 2 days ahead.)
Place the potatoes on one half of a rimmed baking sheet. Using the palm of your hand, press down on each potato to smash to a uniform thickness of about 1/2 inch (the potatoes will split open and the flesh might crumble slightly).
Mix the oil and garlic in a small bowl. Brush half of the oil mixture onto the potatoes and season with salt and pepper. Using a flat spatula, flip the potatoes over, brush with the remaining oil mixture, and season with salt and pepper.
Roast until the bottoms of the potatoes are browned, 15 to 20 minutes. Using the flat spatula, flip the potatoes and sprinkle with the cheese. Place the sausages on the other side of the baking sheet. Roast until the edges and tops of the potatoes are golden-brown, 15 to 20 minutes more. Sprinkle the potatoes with the parsley, if using, and serve.