Place the garlic in a small, microwaveable dish, cover with water and microwave at 100% for 1 minute. In a blender, combine the garlic, chipotles, oils and vinegar (and Worcestershire if you’re using it). Blend until smooth and pour into a small bowl. Taste and season highly with salt, usually a scant teaspoon.
Heat one side of a gas grill to medium-high and the other side to low. Or light a charcoal fire and let it burn until the charcoal is medium-hot and covered with white ash; bank most of the coals to one side. (If you’re using a grill pan, heat it over medium-high and cook the tomatoes until richly grill-marked). Using a brush or an oil sprayer, lightly oil the knob onions and garlic chives, and generously oil both sides of each tomato slice. Grill the knob onions, placing the white knob end on the hot side of the grill and turn regularly to brown on all sides, then moving them to the cooler side to coast along to a beautifully soft sweetness. Sprinkle both sides of the tomato slices with salt and grill them on the hottest part of the grill, about 2 minutes per side (if the tomatoes are soft-ripe, they are harder to work with on the grill). Grill the garlic chives very briefly on the hot part of the grill, turning just until they are wilted. Finely chop the garlic chives into ¼ inch pieces and slice the white knobs into ¼ inch rounds. (Reserve the green part of the onions to use in scrambled eggs or other dishes.)
Arrange a portion of the grilled tomatoes (warm or cooled to room temperature) on a platter. Stir the dressing well and spoon on as much as you like (cover and refrigerate the rest for another salad). Sprinkle with garlic chives, knob onions, black pepper and the toasted sesame seeds and you’re ready to eat.