Boil 150 ml water, and let it cool down until there is no more steam.
While letting the hot water cool down, remove the currants from their stems, rinse, and set them aside in the bowl.
Add the warm water from Step 1 to the currants from Step 2, lightly stir, and leave them for a while (for longer than 10 minutes).
Choose a pan (or wok) large enough to arrange the mackerel fillets in a single layer. Heat up the pan, pour in a generous amount of oil, and spread evenly.
Lightly season both sides of the mackerel fillets with salt and pepper, and pan-fry over medium heat with the skin side down.
In a small sauce pan, melt the butter, and sauté the onion and garlic.
When the onion becomes soft, add the white wine, sugar, and 50 ml of the warm water that was used to soak the currants.
Season with salt and pepper. When the white wine starts bubbling around the edges of the pan, reduce the heat to very low.
Once most of the surface of the mackerel has turned whitish, flip it over.
After 3-5 minutes of pan-frying the mackerel, pour the sauce from Step 8 over the mackerel from Step 9, and simmer over medium heat for 3-5 minutes.
Drain the currants from Step 2 through a sieve, add only the currants to Step 10, and simmer over medium heat for about 5 minutes. Shake the pan from time to time, adjust the taste, and it's done.
Transfer to serving plates, garnish with parsley or other seasonings, and enjoy!
Story Behind this Recipe
I found the first currants of the season at an open-air market. So, I made this dish based on a recipe I found on a website called "Serious Eats".
If the water in which you soak the currants is too hot, it will damage the currants. But if it's not warm enough, the flavor of the currants won't infuse, so be sure to use warm water. I used pink currants for the dish in the photo, but red currants would be pretty as well.