Cut beef sirloin into thin strips against the grain. Add to a bowl and season with oyster sauce, baking soda, garlic powder and white pepper. Marinate for at least 15 minutes.
In a skillet over medium-high heat, add oil and sear for 3-4 minutes. Remove from the pan, add in red curry and toast in the oil for a few minutes then add in onions and green onions. Sautè until fragrant, about 2 minutes. Next, add in green beans and a few dashes of sesame oil.
In a bowl, combine oyster sauce, fish sauce, sriracha, soy sauce and brown sugar. Mix well.
Pour in coconut milk and the oyster sauce mixture. Simmer for about 7-9 minutes, then add the cooked beef back into the curry. Taste and adjust seasonings if needed. Reduce heat, add in cilantro and Thai basil cover and simmer for 5-7 minutes or until the green beans are tender to preference.
Top with red pepper flakes if desired, serve over white rice and enjoy!
