Spinach and Omelet Roll

Have ready a large bowl of ice and cold water. Stir together dashi, mirin, and soy sauce in a large shallow bowl.

Leaving stems attached, divide spinach into 2 piles. Stack spinach leaves and line up bottoms of stems, then tie each pile into a bundle with kitchen string 1/2 inch from ends of stems. Blanch spinach bundles in a large saucepan of boiling salted water 1 minute and transfer to ice water. When spinach is cool, gently squeeze excess water from bundles and transfer to dashi mixture. Marinate at room temperature, turning occasionally, 3 hours.

Stir together cornstarch and water in a glass measure. Add eggs, sake, and sugar and beat with a fork just until blended. If mixture is frothy, let stand until foam subsides. Heat oil in a 12-inch nonstick skillet over moderate heat, swirling skillet to coat, and wipe out excess with paper towels. Pour slightly more than 1/3 cup egg mixture into skillet, swirling to cover evenly, and discard remainder. When edges of egg begin to dry, remove skillet from heat and let stand 20 seconds. Carefully turn egg sheet over (Japanese cooks pick it up by gently working a single chopstick under egg sheet across skillet and lifting it, draped over the chopstick). Cook other side 30 seconds and invert egg sheet onto a work surface.