1. Have a container ready (high temperature proof) and coat with oil lightly, using a paper towel.
2. In a small cooking pot, add water and agar powder. Melt the powder over medium heat, stirring constantly to prevent burning. Heat and stir until the agar powder melts completely. It usually takes about 1 to 2 mins.
3. Add the sugar. Melt the sugar, stirring constantly to prevent burning with a spatula. It will be very foamy and bubbly. Keep on stirring for about 2 to 3 min.
4. Remove from the heat and immediately pour the espresso. Mix well.
5. Transfer into a prepared container through the sieve.
6. Chill in the fridge until it has set. It should be firm enough to cut.
7. Remove from the fridge and cut into small pieces, using the knife or even with your hand (about 2 to 3 cm dices) and place them on a baking sheet. You can also coat the pieces with sugar to make them sweeter.
8. Let the candies sit there for 2 to 3 days (it may even take up to 5 days, as it depends on so many factors : climate, season,...). Eventually their surface should dry out completely. The candies will be crystallized with a jewelry finish. They are crunchy outside, but inside texture is like jelly.
9. You can keep your “kohakutou” in an airtight container for about 2 weeks.