for the filling
1/3 cup cream cheese
1 large egg yolk
1/3 cup confectioners’ sugar
for the topping
1/4 cup all-purpose flour
1/4 cup finely chopped hazelnuts
1/4 cup packed light brown sugar
3/4 teaspoon cinnamon
1/4 teaspoon salt
4 tablespoons cold unsalted butter, cubed
for the muffins
2 large (or 3 medium) sweet potatoes, peeled and cut to 3/4 inch cubes
2 tablespoons butter, cut to small cubes
4 tablespoons brown sugar
1 1/2 cups all-purpose flour
1 teaspoon cinnamon
Pinch of freshly grated nutmeg
Pinch of ground cloves
3/4 teaspoon baking soda
1/2 teaspoon baking powder
1/2 teaspoon salt
2 large eggs
1/2 cup packed light brown sugar
1/2 cup vegetable oil
First make your sweet potato puree. This can be made up to 2 days in advance and refrigerated. Preheat oven to 350F. Place cut sweet potatoes in a small baking dish and sprinkle over the butter and brown sugar. Bake for 20 minutes or until a paring knife inserted into a piece comes out easily. Using a food mill, potato masher or even a food processor, mash the sweet potatoes to a puree. You should have about a cup. Let cool completely.
Next, prepare the filling. In a small bowl, mix cream cheese, egg yolk and confectioners sugar. Cover and freeze until chilled, about 30 minutes.
Then, make the topping. In a small bowl, combine the flour, finely chopped hazelnuts, brown sugar, cinnamon and salt. Work in the butter with your fingers. Press the mixture into small clumps. Refrigerate the topping until chilled, about 15 minutes.
Finally, make the muffins. Preheat the oven to 350F and line a 12-cup muffin tin with liners. In a medium bowl, whisk the flour with the cinnamon, nutmeg, cloves, baking soda, baking powder and salt. In a large bowl, using an electric mixer, beat the eggs with the brown sugar, oil and sweet potato puree. Hand-mix in the dry ingredients until evenly incorporated.
Spoon half of the batter into the prepared muffin cups. Drop heaping teaspoons of the cream cheese filling in the center of each cup and spoon the remaining batter on top. Sprinkle the crumb topping over the batter. Bake for about 30 minutes, until a toothpick inserted in the center of the muffins comes out clean. Let the muffins cool for 10 minutes before turning them out onto a rack to cool completely.