I start by tossing the cubed chicken with fish sauce in a bowl. Then I add cornstarch and stir until each piece is lightly coated.
I heat half the oil in my skillet over medium-high. Once hot, I toss in garlic and ginger and stir for about 30 seconds until fragrant—but not browned.
Next, I add bell peppers, optional red chili, and pineapple into the skillet. I stir fry everything for 3 to 5 minutes until the peppers are crisp-tender. Then I stir in the sweet chili sauce and cook until it’s nicely heated through. I remove this mixture and set aside.
I add the remaining oil to the empty pan, then add the chicken. I stir fry for about 5 minutes until it’s cooked through and golden.
Finally, I return the pepper-pineapple mixture to the pan, toss everything together, and cook until flavors meld. I sprinkle cilantro leaves before serving.