Niku Dofu (Japanese Simmered Beef and Tofu)

Name: Niku Dofu (Japanese Simmered Beef and Tofu)
Prep time: 10 min
Cook time: 20 min
Total time: 30 min
Cuisine: Japanese
Ingredients: 200 g thinly sliced beef (I used rib end cuts); 1 tbsp potato starch (katakuriko); ½ tbsp cooking oil; 4 tbsp Japanese soy sauce (koikuchi shoyu); 100 ml sake; 3 tbsp light brown sugar; 300 ml water; ½ tsp dashi granules; 1 onion ((medium) thinly sliced); 300 g firm tofu (cubed); 100 g enoki mushrooms (roots removed); 10 snow peas