Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius).

Cut the sweet potatoes in half lengthwise.

Pour a few tablespoons oil on a baking sheet, dip the cut side of a

potato in it, and place it on the baking sheet, face down. Continue until all sweet potatoes have been placed. Bake for 30

minutes.

Remove sweet potatoes from oven and flip them over to the other side.

Meanwhile, heat the oil, brown sugar, water, silan or maple syrup, cinnamon, and ginger, if desired, in a saucepan and stir until melted.

Brush cut side of the sweet potatoes with the glaze and bake for another

15–20 minutes, until cooked through.

Combine the flours, hazelnuts, brown sugar, cinnamon, ginger, if desired, and salt in a large bowl and mix. Add the oil and mix until small crumbs form. Place on a baking sheet and bake for 10–12 minutes, until just browning.

Store the sweet potatoes and crumble separately.

Heat the sweet potatoes and place crumble on top right before serving.