Brown the seasoned turkey on medium in a large skillet that can go into the oven (if possible).
As the turkey is browning, you need to start the potatoes (see below)
When the turkey is cooked through and browned slightly, add the 2 cups of frozen vegetables and 2 cups of water, bullion, soy sauce, and lemon juice to the skillet. Make sure to scrape any browned bits from the pan. Mix the 2 tablespoons of corn starch with the remaining 1/4 cup of water and stir to mix. Add the water and cornstarch slurry to the skillet and stir to make it thicker. Stir periodically until the mixture comes to a boil. Turn off the heat.
While the turkey is browning, peel the potatoes and cut them into small uniform cubes- the smaller they are, the faster they cook. Add the cubes to cold water in a pan. Add the frozen cauliflower (I did a rough chop of it so it would be easier to mash in the end) to the water and bring it to a boil over high or medium-high. When it comes to a boil, turn down to medium ad cook until potatoes are soft.
When the potatoes become soft, remove from heat and drain in a colander and transfer to a sturdy bowl or stand mixer. And milk, salt, and butter and mix on medium until blended (you may need to scrape down the sides of the bowl with a spoon or scraper). When blended, add the egg and mix for 30 seconds or so or until combined. The mixture will seem a bit liquid- but it will firm up in the oven.
Spoon the potato/cauliflower mixture over the filling mixture in the oven-proof skillet. Bake in a 350-degree Fahrenheit oven for 30 minutes. Don’t worry if some gravy comes up over the potatoes- this is a rustic dish.