Cut the sweet potato into equal 1/2 inch rounds. Toss in olive oil, salt, pepper and garlic powder.

Set the air fryer or oven temperature to 400.

Set the sweet potatoes on a foil lined baking sheet.

On a separate foil lined sheet pan, lay bacon 1/2″ apart.  Cook bacon at 400 for 10 minutes.  Remove and place on a paper towel.  Drain bacon fat into a bowl and set aside.

Simultaneously, cook the sweet potatoes for 20 minutes.  Remove the sweet potatoes from the oven and let cool to room temp.

Remove sage leaves from stems.  In a small sauce pan over medium heat, add bacon fat and fry 6–8 sage leaves at a time until crisp, about 2–3 seconds. Transfer with a fork to paper towels.

Chop the sage, bacon and walnuts and mix together.

In another small bowl, mix 1 tablespoon of maple syrup and 6 oz mascarpone cheese.  Stir until combined.  Spread 1 teaspoon sweetened mascarpone on each sweet potato crostini, and top with 1 teaspoon of the bacon walnut sage crumble.  

Serve!