Make the Tare Glaze: In a small saucepan, combine the soy sauce, mirin, sake, sugar, and crushed garlic. Bring to a boil, then lower the heat and simmer for 10 to 15 minutes until the sauce reduces, thickens, and becomes glossy and syrupy. Remove the garlic and set the sauce aside in a tall jar or cup.

Prepare the Skewers: Soak the bamboo skewers in water for 30 minutes so they don't burn on the grill. Cut the chicken into uniform 1-inch chunks. Cut the white parts of the green onions into 1-inch pieces. Thread them tightly onto the skewers, alternating meat and onion.

First Grill: Heat a charcoal grill or a heavy grill pan to medium-high heat. Grill the bare skewers for 3 to 4 minutes per side until the chicken is almost fully cooked and slightly charred.

Dip and Caramelize: Dip each hot skewer completely into the thick Tare glaze (or brush it heavily). Return the glazed skewers to the grill. Cook for just 30 to 60 seconds per side until the sugars bubble and caramelize perfectly. Repeat the dipping and grilling one more time for a sticky, massive flavor. Serve hot.