Wash cucumbers and radishes under cold running water. Slice cucumbers thinly (about ¼-inch thick) and radishes to match. Finely chop dill and chives.

In a large mixing bowl, combine sliced cucumbers and radishes with chopped dill and chives. Gently toss together.

In a separate bowl, whisk together whole grain mustard and honey until smooth. Gradually drizzle in olive oil while whisking to emulsify.

Pour the vinaigrette over the mixed salad ingredients and gently toss until well-coated.

Cover with plastic wrap or transfer to an airtight container and refrigerate for at least 30 minutes.