Boil the 2 cut up potatoes in salted water in a medium-sized pot until you can easily pierce them with a fork (about 20 minutes).
Meanwhile, cook the four slices of bacon in a cast iron (or other heavy) skillet until crispy over medium-high heat (about 7-8 minutes).
Transfer the bacon to a paper towel lined plate. Chop when cool.
In the same skillet, saute the diced onion in the bacon grease until softened and browned (about 5 minutes).
Add the apple cider vinegar (2 tablespoons) to the skillet, scraping up any browned bits from the bottom.
Turn off the heat and stir in the whole grain mustard (1 tablespoon), honey (1 tablespoon), kosher salt (1 teaspoon), and black pepper (1/4 teaspoon) until well combined.
One the potatoes have finished cooking, drain them in a colander, and add them to the skillet. Stir to coat in the onion and dressing mixture.
Add the arugula (2 cups) and minced parsley (1 tablespoon) and stir. The heat from the potatoes will wilt the arugula a bit.
Serve warm.
Notes
To make this whole30 compliant, omit the honey.
Make it vegetarian: Omit the bacon, and use 2 tablespoons olive oil or butter to sauté the onions. Make it vegan by using agave or maple syrup instead of honey.
Time saving tip: You can prep the potatoes in advance- just cut and place in a pot and cover with cold water. Refrigerate the entire pot for up to 24 hours and then place directly on your stovetop when you want to cook.
Arugula substitution: You can use another leafy green, such as baby spinach or chopped kale, in place of the arugula. Kale takes a bit longer to cook, as do other greens like collards, so take that into consideration.
The provided nutrition information does not include any added sodium from seasoning to taste, any optional ingredients, and it does not take brands into account. Feel free to calculate it yourself using this calculator or by adding the recipe to Yummly.