Place the tomatoes, mint, garlic, lemongrass, chopped scallion and jalapeno in a blender and pulse until still chunky but releasing liquid.
Line a fine sieve with a double layer of cheesecloth over a large container. Pour the tomato mixture into the sieve and let drain for 2 to 3 hours, or refrigerate overnight.
Season the strained liquid with salt and pepper. Pour into shooter glasses, garnish with the grape tomatoes and sliced scallions.