Slice the English cucumbers into thin ribbons using a vegetable peeler or mandoline. Sprinkle with salt and toss to coat. Let sit in a colander over a bowl for 1 hour to draw out moisture.

In a small bowl, whisk together soy sauce, rice vinegar, peanut butter, honey, garlic, red pepper flakes, and black pepper until smooth and creamy.

Transfer drained cucumbers to a large mixing bowl. Add toasted peanuts and parsley. Drizzle dressing over and toss gently to combine.

Serve immediately for best crunch. If making ahead, refrigerate in an airtight container for up to 8 hours, stirring gently before serving.