In a small bowl, whisk together the soy sauce, mirin, broth, sugar, ginger and garlic. In another small bowl, dissolve the 2 teaspoons of cornstarch in the water. Set aside.

Whisk together the egg white and remaining 2 tablespoons of cornstarch, and brush the skinless side of the salmon with the mixture. Dip in sesame seeds and gently press to coat.

Heat the oil in a large nonstick skillet over medium-high heat. When the oil is hot, place the salmon filets in, sesame seed side down, and cook for about 5 minutes or until golden brown. Turn and continue cooking an additional 3 minutes (for a 1-inch thick fillet) and remove from skillet.

Pour off any oil remaining in the skillet and reduce the heat to medium. Add the soy sauce mixture and simmer for 2 minutes, stirring constantly. Whisk in the cornstarch-water mixture and continue cooking until sauce has thickened, about 1 additional minute. Serve the sauce alongside or underneath the salmon.