Comforting Beef Shepherd's Pie

1. Preheat the oven to 190°C and set an oven rack in the middle position.
2. Place the minced beef, baking soda, 1 teaspoon of the salt, and 1 tablespoon of water in a medium bowl. Mash with fork to combine. Set aside for 20 minutes.
3. While the meat tenderizes, place the peeled, sliced potatoes into a medium saucepan and add just enough cold water to cover them. Bring to a boil over high heat, then reduce the heat to medium-low and simmer for 8 to 10 minutes, uncovered, until the potatoes are soft and fork-tender. Drain the potatoes and return to the saucepan. Place the pan over medium heat and mash the potatoes until they are light and fluffy. Remove the pan from the heat and add the sour cream, butter, half & half, and the remaining teaspoon of salt. Using a potato masher, stir and mash the potatoes with the other ingredients until smooth. Taste and adjust seasoning, if necessary. Set the mashed potatoes aside.
4. Heat a skillet over medium heat. Add the diced onions and carrots to a pan for 6 to 8 minutes with a drizzle of olive oil and cook, stirring frequently, until softened and starting to brown. Add the minced garlic and cook 1 minute more. Add the wine (optional) and increase the heat to high; bring to a boil, scraping any brown bits from the bottom of the pan, until the liquid is reduced by about half. Add the flour and stir until dissolved. 
5. Add the minced beef mixture you had set aside, tomato paste, and Worcestershire sauce. Continue cooking on high heat for roughly 5 minutes, breaking the meat apart with a spoon, until the meat is no longer pink. Add the chicken broth, bring to a simmer, reduce the heat to low, and cook, until thickened, for roughly 2 minutes. Stir in the thyme, pepper, peas and cook until the peas are warmed through. Taste and adjust seasoning, if necessary.
6. Transfer the beef mixture from the skillet to a casserole dish. Dollop the mashed potatoes evenly over the filling. Use a spatula to spread the potatoes evenly over the minced beef mixture and all the way to the edges of the casserole dish. Drag a fork across the top to make ridges and bake for roughly 30 minutes until the filling is hot, the topping is lightly browned, and the edges are bubbly. (For more colour, turn on the grill and grill for the last 5 minutes, or until the top is golden.) Sprinkle with chives and serve.

Make-Ahead Instructions:

The minced beef portion of the recipe can be made a day or 2 ahead of time and refrigerated. Before assembling the pie, reheat the minced beef mixture, adding a little broth if necessary if it seems dry. The mashed potatoes should be made right before assembling and baking the pie.