Heat a pot of water on the stovetop and bring to a full boil. Add the peeled and chopped potatoes and cook for 10 to 15 minutes, or until the potatoes are very soft when poked with a fork. Drain the potatoes into a colander and transfer them back to the pot you used to boil them. Add the butter, Greek yogurt, garlic powder, and sea salt and mash until everything is creamy and well-combined. Taste this mixture for flavor and add more sea salt to taste.

Preheat the oven to 375 degrees Fahrenheit.

Transfer the mashed sweet potatoes to a 13” x 9” casserole dish and spread into an even layer.

Top with grated cheese and bake on the center rack of the preheated oven for 20 to 25 minutes, or until the cheese is melted.

While the casserole is baking, cook the bacon over medium-high heat, stirring occasionally until it reaches your desired level of crisp. 

Once the casserole is out of the oven, sprinkle the cooked bacon over the top along with the chopped green onion.

Serve the cheesy mashed sweet potato casserole with your main dish and enjoy!