Preheat the oven to 400 degrees. \nCook pasta according to package instructions for al dente. Drain, toss with a drizzle of olive oil and set aside. \nAdd 1 tablespoon of olive oil to your pasta pot and heat over medium heat. Once shimmering, add in the mushrooms. Cook until beginning to brown and release some of their liquid, about 3-5 minutes. Stir in the onions and a pinch of kosher salt. Continue cooking, stirring frequently, until the onions have softened and the mushroom liquid has evaporated, about 5-7 minutes more. \nAdd in the butter and, once melted, stir in the flour and Southeast Asia sauce until well combined and smooth. Slowly pour in the stock, about ¼ cup at a time, stirring between each addition and scraping down the sides of the pot as necessary. Repeat until all of the stock has been added. Let simmer over medium-low heat for about 3-4 minutes, allowing the sauce to thicken. \nRemove from the heat and stir in the cooked pasta, mozzarella, parsley, half of the Parmesan and 1 tsp salt. Spread in an even layer in a large baking dish or oven-safe skillet and sprinkle with reserved Parmesan.\nBake for 25-30 minutes, until the edges are golden brown and the cheese is bubbly. If desired, move to the top oven rack and broil for 1-2 minutes for an extra crispy topping! Remove from the oven and garnish with additional parsley. Serve warm.