Preheat the oven to 220°C/430°F. Wash the sweet potatoes, prick the skin with a fork and place them on a baking sheet. Bake for about 45 minutes until they are tender and let them cool.
Peel them with your hands, put them in a bowl and mash them. Add the cheese, salt and pepper to taste. Mix to combine.
Line a baking sheet with parchment paper and place scoops of the mix on the paper. Use your fingers to shape them into cubes.
Fill a bowl with panko or breadcrumbs and dip them one by one to coat. Place them back on the baking sheet. Drizzle each one with olive oil. Bake in a preheated the oven at 220°C/430°F for 15 minutes, flip them over and bake for another 15 minutes, or until golden and crispy.
Optional: Before they are done, melt the butter in a small skillet. Add the herbs and sautée for a few more seconds. Drizzle the cubes with the melted butter as you take them out of the oven, and serve right away.