Step 1
Make the dip: In a large bowl, whisk together the sour cream, milk, onion, chives, parsley, tarragon, lemon juice, and garlic. Season to taste with salt and black pepper. Cover the bowl and refrigerate.
Step 2
Fry the cucumbers: Into a large pot fitted with a deep-fry thermometer, pour 2 inches of oil and turn the heat to medium-high. While the oil heats, in a large bowl, whisk together the cornmeal, flour, baking powder, celery salt, kosher salt, black pepper, garlic powder, onion powder, paprika, and cayenne. Add the cucumbers and toss to coat, shaking off any excess. When the temperature reads 375°F, working in batches, add the cucumbers and fry, turning once or twice, until crisp and golden brown, about 2 minutes per batch. Using a slotted spoon, transfer the fried cucumbers to a paper towel-lined plate. Serve hot with the reserved dip.