1. Slice your chilled kugel evenly. The amount of kugel you have left over will determine how many stacks you can make.
2. In a pan, heat the vegetable oil. Once the oil begins to shimmer, add the slices of kugel and cook until golden brown on both sides. Set the slices aside on a plate while you prepare the other ingredients.
3. Finely chop the shallot. If needed, add a little extra vegetable oil to the pan that you cooked the kugel in. Sauté the shallots over medium-low heat.
4. Toss the mushrooms in with the shallots and turn the heat to medium-high. Once the liquid begins to cook off of the mushrooms and they begin to brown, add a pinch of salt. This is your mushroom duxelles. If you prefer, you can use the leftover brisket instead and skip the mozzarella on top.
5. Turn the broiler on and make sure your rack is low enough that the stack has room to sit under the broiler. On a baking pan lined with foil, place one slice of kugel. Top that with a row of sliced asparagus or green beans. Top that with another piece of kugel and a spoonful of mushroom duxelles (or a piece of brisket). Top with another slice of kugel and add a spoonful of tsimmes or a slice of sweet potato. Top with a final piece of potato kugel and add a slice of mozzarella. Leave the cheese off if you are using brisket. If you need a toothpick or skewer to stabilize the stack, you can push one into the kugel stack being careful that it is not right under the broiler.
6. Place the stack under the broiler until the cheese begins to bubble and brown. Enjoy!