Bake your potatoes in the oven at 375F until just soft, approximately 30 minutes.
Remove the potatoes from the oven and cut in half lengthwise. Place a potato half on top of a towel or pot holder and use a spoon to scoop out the insides of the potato. Try not to cut a hole in the skin itself. You can leave a little potato attached to the skin to hold it together. Place the scooped out potato in a medium mixing bowl. Repeat with all of the potato halves.
Defrost and drain the frozen spinach. Drain and chop the artichoke hearts.
Add the spinach, artichoke hearts, cream cheese, Parmesan cheese, sour cream, garlic powder, and salt to the potato. Mix until just combined. The potato should still be chunky and the mixture thick. You are NOT trying to get a mashed potato consistency (unless you want it well mixed). Adjust the taste with additional salt, black pepper, garlic powder, or sour cream as desired.
Stuff the filling back into each potato skin shell, each with a slight mound on top.
Sprinkle some additional Parmesan cheese on top of each stuffed potato if desired. Put the potatoes back in the oven and bake until they are just starting to brown, approximately 15 minutes. Serve warm.