Prep the ingredients per the instructions above.
Make the marinade: Mix the marinade ingredients in a bowl big enough to hold the beef. Add the beef and mix well. Use your hands to massage everything together. Set aside for 30 minutes, or longer if desired.
Make the rice: Cook the rice according to the directions on the package.
Heat a large skillet or non-stick pan over medium-high heat.
Remove the beef from the marinade, reserving the marinade.
Make Thai tea: Bring water to a boil and mix in Thai tea. Add sugar and gently stir to dissolve sugar completely. Gently boil tea for about 3 minutes. Remove from heat. Allow the tea to steep for at least 30 minutes and allow it to cool. (The more concentrated the tea flavor, the better the taste).
Strain the marinade into a saucepan over medium heat and bring to a simmer. Slowly stir the dissolved cornstarch into the marinade a little at a time (you may not need it all) until the marinade thickens to a smooth consistency then remove and set aside.
Add the oil to the heated skillet or pan and sauté the onions for 2- 3 minutes. Your pan should be hot enough so that the meat sizzles as it touches the pan. Add the beef (in batches if needed) and pan-fry/stir-fry the meat until slightly brown on both sides. Don't put too much meat into the pan or you will end up with a lot of the meat juice leaking out.
Pour the thickened marinade into the pan with the beef and set aside until you are ready to serve.
Finish the rice: Once tender, season with salt and pepper to taste. Cover with a lid to keep warm until serving.
Finish the Thai tea: Strain the tea (preferred to strain through a traditional re-useable cloth filter to remove any sediment). Fill glasses with ice and pour in Thai tea leaving enough room to top with half-and-half.
Portion the beef and rice. Enjoy with kimchi and thai tea.