Niku Udon (Japanese Meat Udon)

Ingredients

• 8 cups water divided
• 2 kombu 6 inches each pieces
• 1 1/2 ounces bonito dried, shaved
• 1/4 cup sake
• 1/4 cup granulated sugar
• 1/4 cup soy sauce
• 1/2 inch fresh ginger piece, grated
• 1 pound beef shaved, sliced as thinly as possible and cut into 1- 1 1/2 inch pieces
• 1/2 cup mirin
• 1/2 cup usukuchi soy sauce
• 1 teaspoon salt
• 4 udon bricks, 8.8 ounces each frozen
• 1 scallion or negi, thinly sliced
• shichimi togarashi