Heat oil in a large frying pan. Add onions and sauté over medium-high heat for five minutes, stirring occasionally. Add mushrooms. Lower heat and sauté an additional minute. Add sweet potatoes and continue sautéing 10 more minutes, stirring occasionally. (If necessary, continue cooking another five to seven minutes, covered, over low heat, to soften the sweet potatoes further.) Set aside.

In a small bowl, combine the soy sauce, sweet chili sauce, silan, and seasonings. Add three to four tablespoons of this mixture to the ground meat. Add one egg and mix until well-combined.

Preheat oven to 400 degrees Fahrenheit (200 degrees Celsius).

Lay out a few pastry dough squares on your work surface. If desired, roll with a rolling pin to flatten slightly. Place a full tablespoon of the meat mixture in the center of a square. Top with a teaspoon of the veggie mixture, gently pressing it down. Bring diagonal corners together to form a triangle, pressing edges together. Alternatively, fill pastry dough circles with a tablespoon of the meat mixture and top with a teaspoon of the veggie mixture. Place on a large baking sheet lined with Gefen Parchment Paper. Continue until meat mixture is used up.

Beat the second egg with a fork for egg wash and brush it over the tops of the knishes. Place baking sheet in oven and bake for 15 minutes or until golden and crispy.

Meanwhile, prepare the garnishing sauce: Add the remaining soy sauce mixture to the veggies in the pan. Add the boiling water. Cook for 10 minutes until well combined and slightly thickened. Spoon over knishes when serving.