Add cashews to a small bowl and cover with boiling hot water. Let sit uncovered for 1 hour.
In the meantime, add potatoes to a large saucepan and cover with room temperature water. Bring to a boil over high heat. Then reduce to medium-high heat so the water is at a low boil. Cook for 15-20 minutes or until tender and a knife easily slides in and out. Then drain and set on a cutting board or counter to cool slightly.
Once the cashews have soaked, drain well and add to a blender along with an additional 1/3 cup (80 ml) water (amount as original recipe is written // adjust if altering batch size). Then add grape seed oil, vinegar, spicy mustard, agave or maple syrup, dill, salt, pepper and garlic. Blend on high, scraping down sides as needed, until texture is creamy and thick but pourable. Add more water if it has trouble blending.
Taste and adjust flavor as needed, adding more dill for herby flavor, garlic for zing/bite, salt and pepper for overall flavor, maple syrup for sweetness, or vinegar for acidity. At this time, you can also add some hot sauce for added spice (optional).
Chop cooked potatoes into bite-size pieces and add to a large mixing bowl along with chopped vegetables. Top with all of the sauce and stir to coat. Garnish with parsley (optional) and serve as is - slightly warm / room temperature - or cover, transfer to the refrigerator, and chill until cold - 4-6 hours or overnight.
Leftovers keep in the refrigerator up to 1 week. Best in the first 72 hours.
*Nutrition information is a rough estimate calculated with all of the dressing and without parsley or hot sauce.