Peel the potatoes and cut them into chunks. Boil them in a large pot of water until the potatoes are soft.
While the potatoes are cooking, place the thawed spinach in a strainer to drain as much water off as possible.
Preheat the oven to 400º Fahrenheit. Spray a 9x13 baking pan with cooking spray.
Drain the water off the potatoes and mash the potatoes.
Add the sour cream, salt, and pepper to the potatoes. Beat the potato mixture until it is fluffy.
Stir the drained spinach into the mashed potatoes.
Spread the mixture in the prepared pan.
Sprinkle the shredded cheese on top of the mashed potatoes.
Bake for 25-30 minutes, or until it is bubbly and the cheese is melted.
If desired, you can bake the casserole for 15 minutes without the cheese so it doesn't melt too much. Add the cheese after 15 minutes and bake for an additional 10-15 minutes.Refer to the article above for more tips and tricks.The calories shown are based on the recipe serving 12, with 1 serving being 1/12 of the potatoes. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information. The information in the nutrition box are calculated through a program and there is room for error. If you need an accurate count, I recommend running the ingredients through your favorite nutrition calculator.**This recipe was introduced to me by a good friend, but it is originally a Taste of Home recipe.