Preheat oven to 450 F
Line a baking sheet with foil and spray with non-stick cooking spray
Cut a small amount off of the bottom of each potato so they can stand upright on the baking sheet
Using a fork, poke small holes all over each potato
Bake for roughly 40 minutes (more or less depending on how big the potatoes are)
Remove from oven and allow to cool completely, or until you're able to handle the potato without burning yourself
Cut the top off of each potato and scoop out the insides using a spoon (a little better than halfway) into a bowl -set aside
Sprinkle a small amount of salt into each potato and return to baking sheet.
Using a large skillet, heat butter and garlic until melted. Toss in spinach and cook until done (roughly 2-3 minutes)
Remove from heat and add heavy cream and Parmesan cheese. Return to heat and allow to cook for 2-3 minutes. Sauce will thicken.
Pour spinach alfredo mixture into bowl of reserved potatoes and mash
Add in 1/4 cup feta and chopped bacon (reserving a small amount) and blend
Pour mixture into hollow potatoes and top with additional feta if desired.
Cook for 10-15 minutes, or until heated all the way through. Top with bacon, cheese, etc