In a large skillet or wok, heat 1 tablespoon of oil over medium heat. Once hot, add the chopped onion and sauté for 3-4 minutes until translucent and fragrant.
Stir in the bite-sized pieces of boneless chicken breasts. Cook for about 5-6 minutes, stirring occasionally, until the chicken is no longer pink.
Add the cubed potatoes and sliced carrots to the skillet. Stir well to combine with the chicken and onion mixture.
Add the yellow curry paste, freshly grated ginger, and minced garlic to the skillet. Stir continuously for about 2 minutes, allowing the spices to toast and release their flavors.
Open the cans of coconut milk and pour them into the skillet. Stir well to incorporate everything, making sure there are no lumps of curry paste.
Bring the mixture to a gentle simmer, then reduce the heat to low. Cover and cook for about 15-20 minutes, or until the potatoes are tender.
In a small bowl, mix the cornstarch with a few tablespoons of water to create a slurry. Slowly stir this mixture into the curry to thicken it. Allow it to cook for an additional 5 minutes.
Stir in the fish sauce (if using), lime juice, and brown sugar. Taste and adjust the seasoning if necessary.
Serve the Yellow Curry over hot cooked rice, garnishing with fresh cilantro and a drizzle of sriracha for those who like a little heat. Enjoy!