1. Combine dill, oil, vinegar, sugar, and mustard in a blender
2. Puree until smooth
3. Transfer to a large bowl and season to taste with the salt and pepper
4. Set this aside…
5. Trim off the bottom of the heads of endive
6. Separate 12 outer leaves
7. Wrap separated leaves in damp paper toweling
8. Refrigerate until ready to serve
9. Cut the remaining endive heads in half lengthwise
10. then
11. Cut crosswise into thin slices
12. Add these to the bowl with the radishes
13. Toss to coat evenly
14. Cover and refrigerate until ready to serve
15. To serve:
16. Place leaves of butter lettuce and reserved endive leaves on the plate
17. Top with the cucumber mixture
18. Drizzle over the plate with any leftover dressing remaining