Combine olive oil, melted butter, garlic, berbere blend, salt, and pepper in a small mixing bowl; stir to combine. Pour 2 tablespoons of the mixture into the bottom of a 2-quart baking dish.
Arrange the sweet potato slices in the dish and brush the potatoes with the remaining olive oil mixture.
Cover with foil and bake for 45 minutes.
Remove the foil and increase the oven temperature to 450˚F. Roast the potatoes for 15 minutes or until they are slightly browned.
For the Parsley Pesto
Meanwhile, combine parsley, walnuts, parmesan cheese, garlic, olive oil, berbere blend, salt, and pepper in a food processor; process until thoroughly incorporated. Taste for seasonings and adjust accordingly.
Brush the tops of the baked sweet potatoes with the parsley pesto, or serve the pesto on the side.
Notes
Even Slices: Use a mandolin slicer to slice the sweet potatoes.
Herbs: You can use basil or cilantro instead of parsley for the pesto. You can also use store-bought varieties.
Different Nuts: Try pine nuts or almonds in the pesto for a different flavor.
Spice Substitutes: If you don't want Berbere, try other spice mixes like garam masala, curry powder, paprika, or Cajun seasoning.
Adjust to Taste: Increase or decrease the seasoning to suit your taste.
Cheese: Swap parmesan with pecorino or Asiago cheese.