Preheat oven to 375°F and set oven rack in the middle position.
Place beef, baking soda, 1 tsp salt and 1 tbsp water in a medium bowl. Mash with your hands to combine and set aside for 20 minutes.
Place potatoes in a large pot covered with cold water. Bring to a boil over high heat, and reduce to a simmer, uncovered until potatoes are soft and fork-tender, 8-10 minutes.
Drain the potatoes and return to the saucepan. Heat over medium until potatoes are dry, mash or use a potato ricer. Add sour cream, butter chunks, half and half and 1 tsp salt, combine until creamy. Set aside.
Heat a skillet or over medium heat, add olive oil, onions and carrots, stir frequently until softened and starting to brown 6-8 minutes. Add garlic and cook 1 minute, add wine and increase to high bring to a boil until liquid is reduced by half. Sprinkle in flour and stir until dissolved. Add ground beef mixture, tomato paste and Worcestershire sauce. Continue cooking on high, breaking meat apart, until the meat is no longer pink. Add chicken broth bring to a simmer and reduce the heat to low, cook until sauce is thick. Stir in thyme, pepper, peas and corn.
Transfer meat to your pie dish and dollop mashed potatoes evenly over the filling. Use a spatula to carefully spread the potatoes evenly over the stew and all the way to the edges. Drag a fork across the top to make ridges.
Place the pan on a baking sheet to catch drips and baking until the edges are bubbly about 30 minutes. To brown the top you can turn of the broiler for the last 5 minutes of baking.