Step 1

Bring ginger, chile, garlic, mirin, soy sauce, sake, sugar, and 1 cup water to a boil in a medium saucepan. Reduce heat and simmer mixture, stirring occasionally, until reduced by half, 15–20 minutes. Let cool. Strain tare through a fine-mesh sieve into a heatproof measuring glass or small bowl; discard solids. Set aside ¼ cup tare. Pour remaining tare into a large resealable plastic bag. Season salmon lightly with salt and place in bag. Seal bag and turn salmon to coat. Chill at least 30 minutes and up to 2 hours (go the full time for the most flavor).

Step 2

Prepare a grill for medium heat. You want moderate heat for fatty fish like salmon so the fat can slowly render while the skin gets nice and crisp. Clean grate well with a wire brush. Just before you set salmon on the grill, fold up a paper towel and hold it with a pair of long tongs. Dip paper towel in oil and wipe down grate.

Step 3

Remove salmon from tare, letting excess drip back into bag; discard tare in bag. Grill salmon, skin side down, brushing occasionally with reserved ¼ cup tare, until skin is lightly charred and crisp, 5–7 minutes. Turn salmon and grill until other side is lightly charred (don’t brush this side with tare), about 5 minutes. Transfer salmon collars to a platter.