Shrimp Ankake Donburi (with Zucchini and Potatoes)



1 tbsp vegetable oil
4 garlic cloves, finely chopped
1 thumb size ginger, peeled and cut into thin strips
1 small onion, finely chopped
1 large potato, peeled and cut bite size (small bites, about ½ to ¾ inch)
2 small zucchini, chopped bite size
12-14 large shrimps (3oz)
2 heaped cups baby spinach
1½ cup dashi broth
3 tbsp soy sauce (for gluten-free substitue with tamari or liquid amino)
½ tbsp sugar
1 tbsp sake
1 tbsp mirin
2 tbsp potato starch (or corn starch) mixed with 2 tbsp cold water
white pepper (optional)