Miso Salmon Skewers

0 Make the Marinade: To a saucepan, add the sake and mirin and bring to a simmer. Reduce by about one third. Add the miso and cane sugar, whisk well, and cook on medium-low for 2 to 3 minutes. Let cool completely.
1 Marinate: Add the salmon cubes to a non-reactive container and pour the cooled marinade over the top. Toss to coat. Cover and refrigerate at least 1 hour, up to 24.
2 Skewer: Thread the salmon cubes onto the skewers, leaving a little space between each.
3 Sear: Preheat a griddle to 425°F (220°C), or use a stainless steel pan over medium-high heat. Add the avocado oil and sear the skewers on all sides, 1 to 2 minutes per side, brushing with marinade from the dish as they cook, until caramelized and golden. Cook to your preferred doneness, from 120°F (49°C) for medium-rare to 145°F (63°C) for fully cooked.
4 Finish: Add the remaining marinade to a pot and boil for at least 5 minutes, stirring frequently. Brush over the cooked skewers.
5 Serve: Serve over white rice with lemon wedges and sliced green onion.