Cut bacon into ½" pieces using kitchen shears and cook them in the cast iron skillet over medium-high heat for 6-8 minutes, stirring often. Toss the sage leaves into the bacon.
Meanwhile, prepare the sweet potatoes. Peel and slice them very thinly with a sharp knife or using a mandolin.
Arrange the sweet potato slices vertically in a 10" round or oval baking dish.
Once bacon is cooked, remove bacon bits from skillet with a slotted spoon and spoon it over the sweet potato slices. Remove sage leaves and discard.
Reduce heat of skillet to medium-low. Add minced garlic to bacon fat and cook for 1-2 minutes.
Pour garlic infused bacon fat evenly over the sweet potatoes. Cover loosely with parchment paper then foil so the aluminum doesn't touch the food.
Bake for 40 minutes or until potatoes are tender. Remove the foil and parchment paper halfway. If after baking, you find that the potatoes have not browned to your liking, simply set your oven to broil for 2 minutes but watch closely so the dish doesn't burn.
The information shown above is an estimate provided for your convenience by an online calculator. It should not be considered as a substitute for a professional nutritionist's advice. Please see our complete Nutritional Information Disclaimer.