Put about equal parts cashews and zucchini into a high-speed blender with the honey. Start with about one tablespoon per approximate 1/2 cup total cashew/zucchini combo knowing you can add more later after tasting.
Add enough water to help with the blending and blend on high until smooth. You want this mixture to be slightly thinner than how thick you want your dressing since we will be adding in the mustard.
Taste just to make sure it’s slightly sweet and creamy.
Add your mustard, starting with about 3 tablespoons worth (a few spoonfuls) for that ~1/2 cup base. Choose any spices you want and add to the blender. This is where this dressing becomes easy to customize: depending on how much mustard flavor you like and which spices you experiment with. I like adding onion powder, garlic, and cumin to draw out those spices from the mustard.
Blend on low if using a course-ground mustard and you want there to be texture in your dressing. Or blend on high to create a smooth texture.
Taste. Assess the flavor. Is there enough mustard? Is there too much mustard? How is the amount of spice? Also assess the thickness.
Adjust by adding more mustard, additional honey to counter any heat, more spices, or even a splash of raw apple cider vinegar to lift the dressing. If it’s too thick, add a splash more water. Blend again.
Do a final tasting before you serve. Enjoy as a dip, sauce, dressing. Stores in the fridge up to a week.