Step 1

Preheat the oven to 325 degrees F. Butter a 2- to 3-quart glass or ceramic baking dish.

Step 2

Arrange the sourdough cubes in a large rimmed baking pan in a single layer. Bake until slightly dried out, about 30 minutes. Transfer to a large bowl.

Step 3

Increase the oven temperature to 400 degrees F.

Step 4

Melt 1 tablespoon butter in a medium skillet over medium-high heat. Add the hazelnuts and a large pinch of salt and cook, stirring often, until nutty smelling and toasted, about 4 minutes. Spoon the nuts onto a clean dish towel and gently but firmly rub the hazelnuts to remove some of the brown skins (it's okay if some of the skins remain). Roughly chop the nuts.

Step 5

Add the remaining 5 tablespoons butter to the skillet and melt over medium heat. Add the celery, garlic, onion, rosemary and 1/2 teaspoon salt and cook, stirring occasionally, until softened, about 10 minutes. Add the currants and cook, stirring, just until plump, about 1 minute. Remove from the heat and cool slightly.

Step 6

Add the hazelnuts and vegetables to the bowl with the bread and mix to combine. Whisk the chicken broth together with the egg, 1/2 teaspoon salt and a few grinds of pepper in a bowl. Add it to the stuffing mixture and stir until well mixed.

Step 7

Spoon the stuffing into the prepared baking dish and bake until hot and golden brown on top, 35 to 45 minutes. Garnish with the rosemary sprig and serve.