Wash and chop spinach roughly, and set aside.
Heat up frying pan with one teaspoon of vegetable oil (you might need more if using a not non-stick pan).
While pan is heating up, mince two cloves of garlic.
Fry the garlic in medium to high heat until it starts to brown.
Add in the spinach, mirin and soy sauce.
When the spinach has cooked (which should be quite fast), turn off the heat and add in one teaspoon of good quality toasted sesame oil. If using a low quality toasted sesame oil, you might need two teaspoons (refer to notes).
Transfer to a plate and garnish with sesame seeds if you have them. This goes well as a side to rice or noodles. Enjoy!