In a large measuring cup, add the tahini, Dijon mustard, lemon juice, apple cider, salt, pepper, and brown sugar. Stir until smooth.
If the mixture feels very thick, add 1 tablespoon of ice-cold water to loosen it slightly. If it looks pourable, hold off on adding more water for now.
Slowly stream in the olive oil with one hand while whisking with the other. The dressing will thicken as it emulsifies. After that, decide if you need more water to thin it.
For reference, I started with 1 tablespoon of water, then added 2 more tablespoons to make the dressing pourable but still creamy. Keep the dressing slightly on the thicker side because the cucumbers will release more liquid after tossing.
Add the chopped fresh dill and stir to incorporate. Taste and adjust with more salt, if needed.
Make the cucumber chickpea salad
Dice the cucumbers into small roll-cut pieces. To do this, trim off the ends, then cut the cucumber on a diagonal. Roll the cucumber about a quarter turn, then cut again on a diagonal. Keep rolling and cutting so you get small, irregular bite-size pieces with more surface area for the dressing to cling to.
Transfer the cucumbers to a large serving bowl and sprinkle lightly with coarse salt.
Drain the chickpeas but do not rinse them. Add them to the bowl with the cucumbers.
When ready to serve, pour in about ½ cup of the dressing. Toss well. Garnish with more chopped fresh dill and sprinkle the blue cheese on top. Serve cold, right away, for the freshest flavor.
Notes
Chickpea tip: For the best flavor, look for chickpeas packed in slightly cloudy, thicker liquid rather than thin, watery liquid. They tend to taste creamier and less flat. Drain but do not rinse before adding them to the salad.
Apple cider substitute: Use unsweetened apple juice. Do not use apple cider vinegar.
Can I use dried dill? Fresh dill gives the dressing a brighter, cleaner flavor. You can use dried dill, but the flavor will be softer and less distinct. Start with ¾ teaspoon, then add up to 1 teaspoon if needed.
How much water should I add to thin the dressing? Tahini brands vary in thickness. You might not need much water at all. Start with 1 tablespoon first, whisk in the olive oil, then add more water only if needed.
Make-ahead and storage: The dressing keeps well in the fridge for up to 1 week. Shake or whisk again before using. The salad is best fresh but can be stored in the fridge for up to 3 days.
Chickpea storage tip: If your jar or carton comes with more chickpeas than you need, save the extra chickpeas with some of their aquafaba in an airtight container. This keeps them creamier in the fridge.