Place 2 cups rice milk and garlic in saucepan. Bring to boil, and reduce to approximately half volume, stirring often. Add salt and pepper.
Mix 2 tablespoons rice milk and cornstarch to make a slurry. Add to reduced mixture, and bring back to simmer. Simmer until thickened. If it’s too gloppy, add a little more rice milk. Keep warm (either turn off heat and cover, or keep on VERY low flame, stirring often.)
Saute beef in a skillet until desired doneness. Remove to a bowl; cover to keep warm.
Turn heat under skillet to low. Deglaze skillet with sauce, scraping browned bits off bottom of pan and into sauce. Adjust seasoning and/or consistency if necessary. Return meat to pan, and toss to coat meat. Serve.
I usually make this with potato wedges, but you could serve over rice or noodles. If you serve over noodles, you may wish to thin the sauce with a little more rice milk to make more of a “gravy” to eat with noodle than a “sauce” for the meat.