Preheat the oven to 375 degrees F. Lightly grease a 1 1/2 quart round casserole dish and line the bottom with parchment paper. (Any similar size round ovenproof dish may be used.)
In a large bowl, combine the breadcrumbs with the milk and eggs. Mix in the green onions, parsley, soy sauce, salt and pepper. Add the ground beef and sausage, and thoroughly combine. (I find this easiest to do with my clean hands.)
Place the mixture in the prepared baking dish, patting to make level.
Bake the meatloaf until the internal temperature reaches 155 degrees F, or about 50-60 minutes. (Precise cooking time will depend on the depth and width of your baking dish.) Cover loosely with foil, and let stand for 10 minutes.
Carefully, pour off any juices from the baking dish, and then run a knife around the sides to loosen. Place a flat serving platter over the casserole dish, and flip to invert the meatloaf onto the platter. (I place two slightly overlapping pieces of foil or parchment paper between the meatloaf and the platter before flipping. These will keep the platter clean while the meatloaf is being iced and can be easily pulled from opposite sides once finished.)
Using a spatula, spread the mashed potatoes over the meatloaf as you would icing. If any juices leak onto the platter, dab them with a paper towel.
Place the tomatoes, stem ends down, in a ring around top of the “cake” to resemble cherries. Cut the meatloaf into wedges, and serve immediately. If not serving immediately, allow the meatloaf to sit at room temperature for up to two hours. Reheat at 300 degrees for 15-20 minutes or until hot.