How to Make It
In a large saucepan of salted boiling water, cook the Swiss chard until bright green and tender, 1 minute. With a slotted spoon, transfer the chard to a colander to drain. Repeat with the spinach. When the greens are cool enough to handle, gently squeeze out the excess water, then coarsely chop them.
In a bowl, combine the soy sauce, fish sauce and sesame oil. In a large skillet, melt the butter and remove from the heat. Add 3 tablespoons of the soy mixture and the greens to the skillet and toss to coat. Transfer the greens to a large plate to cool slightly.
Form the greens into 8 mounds on a platter. Spoon the remaining soy mixture over the mounds, garnish with the toasted sesame seeds and bonito flakes and serve.
Bonito flakes are available at Asian or specialty food markets.