Total: 45 minutes
for the tare:
5 ounces chicken wing tips (or any chicken trimmings)
2 cups mirin
2 cups sake
2 cups soy sauce
3 1/2 ounces Japanese black sugar
1 (1-inch pieces) ginger
1 garlic clove
8 large egg yolks for the skewers:
10 ounces ground chicken thighs
5 tablespoons panko breadcrumbs
1 teapsoon kosher salt
4 scallions, finely chopped
3 shiso leaves, finely chopped
8 bamboo skewers soaked in water for 2 hours
1. Make the tare: Heat a medium saucepan over high heat. Add the chicken and cook, turning as needed, until golden and caramelized, 10 minutes. Add the mirin and sake and cook until thick, 15 to 20 minutes. Add the soy sauce, scallions, ginger, and garlic and cook 2 minutes more. Add the sugar and cook until dissolved, 5 more minutes. Strain, discarding solids, and cool the tare completely.
2. Make the skewers: In a medium bowl, mix the chicken, panko, salt, scallions, and shiso. Tradition says to mix it 16 times clockwise then 16 times anti-clockwise to get the right consistency.
3. Divide the meat into 8 equal pieces and, using your hands, press the meat around the skewer.
4. Light a grill. Add the skewers to the grill and cook, turning as needed, until almost cooked through, 8 to 10 minutes. Brush with the tare and cook until caramelized and done, 4 minutes longer. Transfer the skewers to a serving platter and keep warm.
5. Divide the egg yolks between 8 ramekins. Pour some of the tare over each and allow them to sit for 5 minutes to cure slightly before serving with the skewers.