Line a baking sheet with parchment paper. Lay eggplant slices on the baking sheet and sprinkle lightly with salt. Let sit 30 minutes, then pat dry.
Make an assembly line with three plates: potato starch on the first plate, eggs on the second, and ground almonds on the third.
Dredge eggplant slices in that order, coating completely. Return to the baking sheet.
Preheat oven to 350 degrees Fahrenheit.
Coat the bottom of a large sauté pan with oil and heat over medium heat. Add all three diced onions (one for the chicken mixture and two for the mushroom sauce). Sauté until lightly browned. Remove one-third of the onions to use now and set aside the sauté pan to continue the sauce later.
In a bowl, combine one-third of the sautéed onions, chicken, mashed potato, egg, salt, and pepper.
Place one scoop of the mixture on each eggplant slice. Cover and bake 45 to 55 minutes.
If you don’t have a cookie scoop, you can use a small ladle to portion out the chicken mixture.
Towards the end of the baking time, return the sauté pan with two-thirds of the sautéed onions to the stove and turn to medium heat.
Add mushrooms, salt, pepper, and paprika (if using), and sauté three to four minutes.
Add stock and simmer two more minutes.
To serve, plate each baked eggplant slice with chicken mixture and top with warm mushroom sauce.