Pour half of the remaining sauce (so 1/4 of the original amount) into a 9x13” glass baking dish, and spread out into an even thin layer.
Heat a lightly oiled pan on medium-low heat. Ladle enough lettuce pancake batter into it to make a 6” round pancake. Cook like a typical pancake, flipping once the top has turned dark green instead of light green.
NOTE: if the first pancake is too thick, add more water. If it’s too thin and tears easily, add a little more flour. This recipe has some wiggle room, so you can make several imperfect test pancakes and still have enough to finish the dish.
Once you have a pancake, transfer it onto a plate. Ladle the next batch of batter into the hot pan, then put about 1/4 cup of filling onto the first pancake. Roll, and transfer (seam side down) into the sauced baking pan.
By the time your pancake is stuffed and in the baking dish, the one in the pan should be ready to flip. Continue making and stuffing pancakes until the baking dish is full. You should be able to fit 10-12 rolls depending on how large you make them.
Top the rolls with the remaining sauce. Bake at 350 degrees Fahrenheit for 15 to 20 minutes.
Serve the rolls, optionally garnishing with toppings of your choice. (I used a mixture of beech and enoki mushrooms simply and lightly sautéed with butter and salt.)