Add 5 quarts of water to a large pot and bring to a boil. While the water is boiling fill a large bowl with 2 cups ice and 4 cups water. To the boiling water, add the salt, stir, and add the broccolini. Cook for two minutes. Remove the broccolini and immediately place in the ice water. Do not dump the water.
To the same water as the broccolini was cooked, and your pasta and cook according to directions, but remove 1 minute earlier. Place pasta on a sheet pan to allow to cool. Save ½ cup of pasta water. While pasta cools begin making the dressing.
To a large salad bowl, add a tablespoon of pasta water, mayonnaise, vinegar, mustard, honey, red pepper flake, salt and pepper. Whisk to combine.
To the dressing add the onion and toss until coated in dressing and pieces separate. Then add the parsley and mix. Add the broccolini and cooked pasta and mix into dressing. Add the chopped cashews and toss. Chill for at least 30 minutes prior to serving.
This salad will keep in the refrigerator for up to 5 days.