To toast the walnuts, heat a small pan over low-medium heat. Once the pan is hot, add the chopped walnuts and toast them until they're fragrant and lightly golden, tossing them occasionally to prevent burning. Remove the pan from the heat and set it aside.
Place all of the vinaigrette ingredients in a small bowl and whisk until well combined. Taste and adjust seasoning to you preference.
Transfer all ingredients, from the cucumbers to the toasted walnuts, into a large serving bowl. Drizzle it all with the vinaigrette and toss to coat. Add some cracked black pepper and give it another toss.