Peel a medium butternut squash. Cut through to separate the neck of the squash from the rounded base. Slice the neck in half from top to bottom, then slice into half moons. Slice these half-moons in strips, then into cubes. Try to keep the cubes roughly the same size. Of course, they won't all be perfectly shaped cubes! Do the same with the rounded base after removing the seeds with a spoon.
Combine olive oil, maple syrup, smoked paprika and honey in a medium bowl, whisking to combine. Add the squash cubes and toss to coat evenly.
Use an oil mister or brush to coat the grill pan lightly. Preheat your air fryer to 390°F. for 3 minutes, then add the squash cubes in a single layer. Depending on the size of your air fryer, you may have to fry the squash in batches.
Air fry for 5 minutes, remove the grill pan, toss to redistribute, then air fry for 1 minute more or until squash is fork-tender and has crispy edges. Cooking time will depend on the type of air fryer you have. Add more time if necessary.
Meanwhile, melt butter in a skillet over medium heat. Add the fresh sage leaves and cook for a few minutes until almost crisp. Remove to a paper towel to drain.
Transfer cooked squash to a serving bowl, top with crisp sage leaves and feta cheese crumbles and serve right away.
This butternut squash side dish will be best when served fresh and hot. If you have leftovers, cover and refrigerate promptly.To reheat, spread out on an oiled or parchment-paper-lined baking sheet and heat in the oven at 375°F. for 10 - 15 minutes or until heated through and slightly crisp.