Step 1

Drizzle the rinsed udon noodles with the 2 teaspoons sesame oil, then toss until evenly coated; set aside. On a 6-quart Instant Pot, select More/High Sauté. Add the sesame seeds and toast, stirring often, until golden brown and fragrant, about 10 minutes. Press Cancel to turn off the pot. Using potholders, carefully remove the insert from the housing and pour the seeds into a small bowl; return the insert to the housing.Select More/High Sauté. Add the remaining 2 tablespoons oil, shallots and the scallion whites. Cook, stirring often, until the shallots are lightly browned, 3 to 5 minutes. Add the garlic and cook, stirring, until fragrant, about 30 seconds. Stir in the sesame seeds, oyster sauce, hoisin and 1 tablespoon of chili-garlic sauce, scraping up any browned bits. Add the mushrooms and stir to combine, then distribute in an even layer.

Step 2

Press Cancel, lock the lid in place and move the pressure valve to Sealing. Select Pressure Cook or Manual; make sure the pressure level is set to High. Set the cooking time for 12 minutes. When pressure cooking is complete, quick-release the remaining steam by moving the pressure valve to Venting. Press Cancel, then carefully open the pot.

Step 3

Select More/High Sauté and bring the mixture to a boil. Cook, stirring often, until the mixture begins to sizzle, about 5 minutes. Stir in the ginger and the remaining 1 to 2 tablespoons chili-garlic sauce, then cook until fragrant, about 30 seconds. Press Cancel to turn off the pot. Stir in half of the scallion greens, then let stand for 5 minutes. Meanwhile, divide the noodles among individual serving bowls. Spoon on the sauce, then sprinkle with the remaining scallion greens and drizzle with chili oil (if using).