In a saucepan, reduce the vinegar on low heat until the balsamic is about 1/3 or less of its original volume. Cook's Note: The vinegar should be thick and syrup-like, so be careful not to burn it, there is a fine line, the slower the better.
Place to the side and cool.
Preheat the oven to 350 degrees F and preheat the grill.
For the gratin:
Set the mandoline blade to about 1/8-inch thick. Cut the zucchinis into thin strips and toss in lemon juice and add a pinch of salt. Set aside. Put the miso paste in a food processer and turn it on, slowly adding olive oil until it is smooth and uniform.
Using a soft rubber spatula spread the paste onto the zucchini strips and layer them in a regular lasagna pan, overlapping each row. Repeat the process until the pan is 3/4 full and bake until top starts to brown and it pulls away from the sides. Cut into 8 pieces.
Oil the grill grates. Cut the peaches in half and grill until they have nice solid grill marks. Cool and slice into wedges.
Place 1 piece of gratin in the center of the plate and top with slices of grilled peaches, some sea beans and julienned shiso.
Finish with a drizzle balsamic reduction and a sprinkle of toasted sesame seeds.