Pat the shrimp dry with some paper towels and then toss them in a large bowl with ½ teaspoon Diamond Crystal kosher salt and ¼ teaspoon black pepper.
Heat a large heavy bottomed skillet over medium high heat. When the pan is hot, add 1 tablespoon of extra virgin olive oil. Place the shrimp in a single layer in the pan.
Cook the shrimp for about 1 minute or until pink on the bottom. Then, flip each one to cook for another minute or until cooked through. Don’t overcook the shrimp or they’ll turn rubbery! Transfer the cooked shrimp to a clean bowl.
In a measuring cup or small bowl, whisk together the champagne vinegar, Dijon mustard, ½ teaspoon of Diamond Crystal kosher salt, and ¼ teaspoon of freshly cracked black pepper. Slowly whisk in ¼ cup of extra virgin olive oil until a uniform suspension forms. Taste and adjust seasoning with more vinegar, olive oil, salt, and/or pepper if needed.
Spoon 2 tablespoons of the dressing over the cooked shrimp and toss well. Set aside to let the flavors meld and for the shrimp to cool down a little.
In a separate large bowl, add the arugula and shaved fennel. Season with salt and pepper. Add salad dressing to taste and toss well to combine.
Divide half the salad greens onto four individual plates. Then, distribute half of the shrimp, orange segments, avocado, and pistachios to each plate.
Divvy up the the remaining salad greens and the rest of the toppings. Garnish with Quick-Pickled Red Onions if desired. Season to taste with salt, pepper, or extra salad dressing. Serve immediately!