Make the dressing: Combine the buttermilk, sour cream, mayonnaise, 2 tablespoons each chives and dill, the lemon juice and hot sauce in a blender. Blend until very smooth. Season with salt and pepper. Refrigerate until ready to use.
Cook the bacon in a medium skillet over medium heat, stirring occasionally, until browned and crisp, 5 to 7 minutes. Remove with a slotted spoon to a paper towel-lined plate to drain.
To serve, arrange the lettuce leaves on a platter and top with the tomatoes, radishes, cucumber and bacon. Season with salt and pepper. Drizzle most of the dressing over the salad and serve the remaining dressing on the side. Sprinkle with the remaining 1 tablespoon each chives and dill.