1 medium Yukon gold potato (about 6–8 ounces), cut into rough 1-inch chunks
1 teaspoon salt, divided
1 tablespoon butter
For the pie
1 teaspoon olive oil
1/2 medium onion, diced
1 small carrot, diced
Pinch salt
1 fat clove garlic, minced
6 ounces lean ground sausage
1 teaspoon flour
1 tablespoon tomato paste (optional)
1/2 teaspoon dried thyme
1/3 cup chicken stock, vegetable stock, or water
Splash white wine
1/4cup frozen peas
Freshly-grated Parmesan cheese
Instructions
First, make the potatoes. Place potato chunks into a saucepan and cover with cold water. Bring to a boil over high heat, add 1/2 teaspoon salt, and cook until potatoes are just tender, about 12 minutes. Use a slotted spoon to remove potatoes to a shallow bowl, reserving cooking water in saucepan. Mash potatoes with butter, remaining half teaspoon salt, and 1 tablespoon cooking water, until smooth. Add additional cooking water if needed for a smooth (but not runny) consistency. Set aside.
Meanwhile, heat oven to 400°F.
Add olive oil to a small, oven-safe skillet over medium-high heat. When it shimmers, add onion, carrot, and pinch of salt and cook until onions begin to soften, about 4 minutes. Add garlic and meat and cook, stirring, until meat is broken up and the pink color has just begun to fade, about 4 minutes. Add flour and cook, stirring constantly, 1 minute. Add tomato paste and thyme, stirring until evenly distributed and no tomato paste lumps remain, about 30 seconds. Add broth or water and bring mixture a boil. As soon as it bubbles, remove skillet from heat, stir in peas, and then allow mixture to cool for 5 minutes.
Spoon mashed potatoes over meat mixture, then gently press into a somewhat even layer. Use the tines of a fork to create little ridges across the top, sprinkle with parmesan cheese, and bake 15 minutes. Adjust oven heat to broil and cook 3 additional minutes, or until potato ridges are beautifully browned at the tips.