Preheat oven to 350°F.
Rub the whole potatoes with the olive oil and season with salt. Place on a baking sheet. Bake for 50–60 minutes, or until a fork inserts easily into the potato. Let the potatoes cool for 10 minutes.
While the potatoes cool, heat 2 teaspoons of olive oil in a medium sauté pan over medium heat. Add the spinach. Cook, stirring occasionally, until the spinach is wilted.
Place the sour cream, mayonnaise, cream cheese, and ¼ cup milk in a large bowl.
Halve the potatoes and scoop the insides out with a spoon, leaving a ¼ inch edge on the potato skin. Place the insides of the potatoes in the large bowl with the sour cream and other ingredients.
Sprinkle the potato skins lightly with salt and place back on the sheet pan.
Using a hand mixer, mix the insides of the potatoes with the sour cream mixture until smooth. Add an additional ¼ cup milk if necessary to get a creamier consistency.
Fold in the artichoke hearts, spinach, ½ teaspoon salt, and half the parmesan cheese.
Divide the potato mixture evenly among the potato skins. Top with the remaining parmesan cheese.
Bake for 10–15 minutes, or until the potatoes are warmed through and the cheese is melted. Garnish with fresh parsley if desired, and serve immediately.