For the tuna burgers: 3 lbs. yellowfin tuna fillets, chopped fine by hand, remove sinew 1 tablespoon minced garlic 1 tablespoon Dijon-style mustard 1 tablespoon cayenne olive oil for brushing the tuna burgers 6 egg-bread or other soft rolls, halved horizontally, buttered lightly, and toasted Make the glaze: In a heavy saucepan cook the teriyaki sauce, the stock, the ginger root, the garlic, the honey, the mustard, and the vinegar over moderate heat, stirring occasionally, for 30 minutes, or until the glaze coats the back of a wooden spoon. Strain the glaze through a fine sieve set over a bowl and reserve it. Make the tuna burgers: In a bowl combine well the tuna, the garlic, the mustard, the cayenne, and salt and pepper to taste and form the mixture into six 1 -inch-thick patties. Heat a dry large heavy skillet, preferably cast iron, over moderately high heat and in it saute the patties, brushed with the oil in batches, for 5 to 6 minutes on each side, or until they are just cooked through. Transfer the tuna burgers to the buns and spread the reserved glaze evenly over the top of each burger. Serves 6. fish 30