Toast the sesame seeds in a dry skillet over medium heat until slightly golden, about 1 minute. Immediately transfer to a bowl to cool.
Preheat the broiler. Toss the mushrooms with the sesame oil on a baking sheet and broil until golden and crisp, about 5 minutes. Pour off any excess liquid, season with salt and pepper and set aside to cool.
Put the corn on a baking sheet; broil, turning occasionally, until slightly charred, 5 to 8 minutes. Set aside to cool.
Make the vinaigrette: Whisk the vinegar, 1/4 teaspoon salt and a few grinds of pepper in a large bowl. Gradually whisk in the grapeseed oil to make a smooth dressing. Stir in half of the cilantro, the shallot and 2 tablespoons toasted sesame seeds. Add the tomatoes, radishes, jalapeno, mushrooms and the remaining cilantro; toss to coat. Season with 1/2 teaspoon salt and a few grinds of pepper.
Cut the corn kernels off the cobs; scatter them over the salad and gently toss to combine. Sprinkle with the remaining sesame seeds.