Step 1

For the potatoes: Add the potatoes to a large pot and fill with cold water until completely submerged. Season the water with 2 tablespoons of the kosher salt. Bring the water to a boil and cook until the potatoes are fork tender; start checking for doneness at 20 minutes. Drain the potatoes in a colander and set aside.

Step 2

In the same pot over medium heat, add the heavy cream, butter, milk, white pepper and remaining 3/4 teaspoon kosher salt. Heat until the butter is melted and whisk to combine. Using a ricer, rice the potatoes into the cream mixture. Gently stir to combine, being careful not to over-mix to avoid the potatoes becoming gummy. Cover the pot and set aside off heat while you make the chicken.

Step 3

To make the chicken: Arrange an oven rack in the middle position. Preheat the oven to 450 degrees F. Line a baking sheet with aluminum foil.

Step 4

Evenly space the 4 lemon slices on the prepared baking sheet. Place a quarter of the leeks next to each slice to create platforms for each chicken quarter. Place one chicken quarter on top of each platform. Season the chicken with salt and pepper. Roast for 25 minutes.

Step 5

Meanwhile, make the garlic butter. In a small saucepan over low heat, add the butter and heat until melted, about 2 minutes. Add the garlic to the butter and heat until the garlic is softened and fragrant, 2 to 3 minutes.

Step 6

After 25 minutes, remove the chicken from the oven. Lower the oven temperature to 375 degrees F.

Step 7

Using a pastry brush, brush the par-cooked chicken all over with the garlic butter. Add the carrots to the baking sheet with the chicken and toss to coat in the pan drippings. Return the chicken and carrots to the oven and roast until a meat thermometer inserted into the thickest part of the leg registers 165 degrees F and the chicken skin is golden brown and crispy, about 20 minutes more. Transfer the chicken, carrots and leeks to a plate or baking sheet.

Step 8

To make the chicken jus: Pour the pan drippings into a small saucepan over medium heat. Add the chicken stock incrementally and whisk to combine until the desired consistency is reached. Cook until just bubbling, 3 to 4 minutes. Taste for seasoning and add salt and pepper.

Step 9

To plate the chicken: In a shallow bowl, add a heaping spoonful of mashed potatoes. Ladle in a spoonful of the chicken jus. Nestle a piece of chicken into the bowl along with a carrot and a leek. Season with flaky salt.