2. In a large bowl, combine the mashed potatoes, 1 cup of the pot roast, and the onion, egg, flour, and parsley. Stir to combine thoroughly. Season with salt and pepper to taste and stir to further combine.
3. Form the potato mixture into 4 cakes about 3 inches in diameter and 1/2 inch thick and refrigerate for about 15 minutes.
4. Heat the olive oil and butter in a large nonstick or cast-iron skillet over medium heat. Add the potato cakes, reduce the heat to medium, and cook about 3 minutes per side, until golden brown and crispy. Place in the oven to keep warm.
5. Make Poached Eggs (see recipe here).
6. Toss greens with 1/4 cup of vinaigrette. Divide the dressed greens evenly among 4 plates, reserving some for a garnish.
7. Place 1 potato cake on each bed of dressed greens. Top with 1 or 2 poached eggs and about 1/4 cup of the remaining pot roast. Drizzle each plate with the remaining dressing and top with additional dressed greens, if desired. Serve immediately.
Makes 4 servings
Adapted from Sara Foster's Southern Kitchen (Random House, 2011)