This salad looks best when the tomato slice and the goat cheese slice are about the same size. So if you can only find goat cheese in small logs, you may want to serve 2 goat cheese rounds to each diner and perch them on slices from small tomatoes. Be sure you take all the stems off the herbs carefully so your guests can enjoy just the soft leaves.
In a small, shallow bowl, mix the breadcrumbs with salt and pepper to taste. Add the water and work it in with your fingers to moisten the crumbs lightly. In another small, shallow bowl, beat the egg just until blended.
Dip one flat surface of each goat cheese round in the egg, and then in breadcrumbs, patting the crumbs in place. Repeat on the other flat surface, leaving the sides of the rounds uncoated. Refrigerate the coated cheese rounds for about 15 minutes.
Center the tomato slices on 4 salad plates. Season with salt and pepper.
Heat a large nonstick skillet over moderately high heat. Add the 2 tablespoons olive oil. When the oil is almost smoking, add the cheese rounds, one coated side down. Cook until lightly browned, about 45 seconds, then turn and cook on the second side until the cheese just feels quivery, about 45 seconds longer, depending on the thickness of the rounds. Place a cheese round on each tomato slice.
In a bowl, toss the herbs with a splash of red wine vinegar, a light drizzle of olive oil, and salt and pepper to taste. Mound the herbs on top of the cheese, dividing them evenly. Serve immediately.