Irish Turkey and Ham Cottage Pie

Trim the bottom 2-inches from 1 large bunch parsley. Tie the trimmed stems together with kitchen twine, or wrap in cheesecloth and tie up into a bundle. Place the parsley stems, 3 cups of the whole milk, and 2 bay leaves in a small saucepan. Bring to a simmer over low heat.

Turn off the heat. Cover and let the flavors infuse. Meanwhile, finely chop the leaves and tender stems from the remaining parsley until you have about 1 cup. Juice 1 small lemon until you have 1 1/2 tablespoons.

Peel 2 1/2 pounds russet potatoes and cut into 1-inch pieces. Transfer to a medium pot. Trim and halve 2 medium scallions and add to the saucepan. Add enough cold water to cover the potatoes, then add 1/4 cup of the heavy cream if using and 1 1/2 teaspoons of the kosher salt. Bring to a boil over medium-high heat. Reduce the heat to maintain a lively simmer and cook until the potatoes are tender, 15 to 20 minutes. Meanwhile, start the filling.

Bring a large pot of water to the boil over medium-high heat. Meanwhile, halve, core, and cut 2 pounds green cabbage into 1/4-inch shreds until you have 7 packed cups (about 14 ounces). Cut 1 medium bunch scallions crosswise into 1/2-inch pieces. Finely grate 1 large garlic clove. Cut 12 ounces cooked ham into 1-inch chunks, removing any excess fat. Cut 1 pound turkey breast or tenderloin into 1-inch pieces.

Add 1 teaspoon of the kosher salt to the boiling water. Add the cabbage and cook for 2 minutes. Drain. Once cool enough to handle, transfer the cabbage to a clean kitchen towel or paper towels, wrap it up, and squeeze out the excess liquid with your hands. Return the cabbage to the pot and cook over medium heat, stirring occasionally, until slightly browned at edges and the moisture is evaporated, about 5 minutes. Transfer the cabbage to a plate; reserve the pot.

Place 4 tablespoons unsalted butter and 3/4 cup milk in a small microwave-safe bowl. Microwave until the butter is melted and the milk is warm, 1 to 2 minutes. (Alternatively, place in a small saucepan over medium-low heat for 2 to 3 minutes.)

When the potatoes are ready, drain and discard the scallions. Return the potatoes to the pot over low heat for 2 minutes, stirring regularly (this dries out potatoes and yields a fluffier mash). Remove the pot from the heat. Pour half of the butter-milk mixture and the remaining 1/4 cup heavy cream if using over the potatoes and start mashing with a potato masher. Add the remaining butter-milk mixture in 2 tablespoon increments, using a fork to beat, until smooth and creamy. Season with the remaining 1 teaspoon kosher salt and 1/2 teaspoon white pepper.

Arrange a rack in the top third of the oven and heat the oven to 400℉.

Remove, but reserve, the parsley stem bundle and bay leaves from the infused milk. Melt 1 stick unsalted butter in a medium saucepan over medium heat. Add 1/2 cup all-purpose flour and cook, stirring continuously for 2 minutes. Add 1 teaspoon kosher salt and 1/2 teaspoon ground white pepper.

Increase the heat to medium-high. While whisking continuously, slowly pour in the infused milk and whisk until smooth. Add the parsley stem bundle and bay leaves. Reduce the heat to medium-low heat and simmer, stirring occasionally, until thickened, about 5 minutes.

Discard the parsley bundle and bay leaves. Reserve 2 tablespoons of the chopped parsley for serving and stir the remaining parsley into the sauce. Simmer, stirring occasionally, until very thick, about 5 minutes. Remove the saucepan from the heat. Stir in 1 tablespoon of the lemon juice.

Heat 1 tablespoon olive oil in the pot the cabbage was cooked in (no need to wash) over medium-high heat until shimmering. Add the turkey in a single layer and cook, stirring occasionally, until just cooked through and the edges are browned, about 5 minutes. Reduce the heat to medium. Add the scallions and garlic and cook, stirring continuously, until garlic is fragrant and the scallions have softened slightly, 2 to 3 minutes.

Add the ham and cabbage, season with 1/2 teaspoon kosher salt and 1/2 teaspoon ground white pepper, and cook until all moisture has evaporated, 3 to 5 minutes. Remove the pot from the heat. Add 2 cups of the parsley sauce (it may have thickened significantly) and stir to combine; reserve the remaining sauce for serving.

Coat a 2 1/2-quart baking dish (or a deep 9-by-9-inch baking pan) with unsalted butter. Transfer the cabbage filling to the baking dish and spread into an even layer. Spoon the mashed potatoes on top and spread to cover the filling. Use either a spoon to make swirls or a fork to make striped patterns on the surface (this creates a crispy texture).

Hold a box grater or Microplane over the potatoes and finely grate 1 ounce aged cheddar, Dubliner, or Parmesan cheese over the potatoes to cover the surface. Place the baking dish on a baking sheet.

Bake until the cheese is melted and the topping is golden-brown, about 35 minutes. For an extra-crispy topping, broil on high heat for 3 to 5 minutes. Let rest for 10 minutes before serving.

Rewarm the remaining parsley sauce in the microwave for 1 to 2 minutes. (Alternatively, simmer in a small saucepan over medium-low heat for 2 to 3 minutes.) If the sauce is too thick, thin it out with up to 1/4 cup of the remaining milk. Taste the sauce and season with the remaining 1/2 tablespoon lemon juice, kosher salt, or ground white pepper as needed.

Sprinkle the cottage pie with the remaining 2 tablespoons parsley. Serve with the parsley sauce.