Wash and peel the 2 carrots, 1 yellow potato, and 1 yellow onion. Clean the 1/4 green cabbage and discard any wilted outer leaves.
Cut the 2 carrots and 1 yellow potato into thin matchsticks so they steam evenly. Thinly slice the 1 yellow onion and 1/4 green cabbage, and mince the 2 garlic cloves.
Finally, slice the 250 g Top Sirloin or Flank Steak beef into bite-size pieces.
The Handmade Noodles
In a mixing bowl, combine the 320 g all-purpose flour and 240 ml water. Mix to form a dough.
On a floured wooden cutting board, knead the dough well until smooth and elastic. If it is too sticky, add a little flour; if crumbly, add water.
Cover the dough with an inverted bowl or wrap in plastic and allow to rest for 15 minutes. This helps relax the gluten and makes it easier to roll out.
Divide the rested dough into 4 equal pieces. Keep three covered, and roll one piece of dough into a thin sheet on your floured surface, making sure the bottom does not stick. Grease the top of the sheet with some of the 1 Tbsp. vegetable oil, making sure all parts are completely covered to prevent sticking.
Loosely roll the sheet up, long side to long side. Using high-quality cooking knives, quickly cut the roll into thin strips about 1/4 inch (6 millimeters) wide. Gently shake the strips loose with your fingers to separate them. Repeat with the remaining dough.
The Stir-Fry
Heat 1 Tbsp. vegetable oil in a frying pan over high heat. Sear the beef until a dark golden crust forms before adding the onion. Cook until the onion is softened.Denis's Tip: Achieving a hard sear without moving the meat (the Maillard reaction) creates the deep flavor profile that characterizes an authentic Tsuivan.
Add the prepped 2 carrots, 1 yellow potato, 1/4 green cabbage, and 2 garlic cloves. Cook until they are just starting to soften, about 5 minutes.
The Steaming
Combine 180 ml water and 1 Tbsp. soy sauce, pour into the pan, and bring to a boil. Reduce to a simmer.
Arrange the sliced noodles in an even layer over the top of the meat and vegetables, leaving a small hole in the center to allow steam to escape.
Cover tightly with a lid and steam the noodles until cooked through, about 15 minutes. If all the water has evaporated before the noodles are cooked, add a little bit more.
Once cooked, remove the lid and gently fan the noodles using a paper fan or the pot lid to help dry out the top layer. Use a fork to gently fluff and separate the noodles. Add the 1 Tbsp. unsalted butter and lightly toss all the ingredients together. Season with ½ tsp. salt and ¼ tsp. freshly ground black pepper to taste.
The Serving
Serve hot immediately, topped with the 2 green onions. Enjoy your authentic Mongolian Tsuivan Noodles [цуйван]!