Crunchy Vanilla Hazelnuts

Makes about 6 cups.

To make espresso hazelnuts, fold 1/2 cup plus 2 tablespoons freshly ground espresso beans into the egg white mixture, just before adding hazelnuts.

6 cups hazelnuts (about 1 3/4 pounds)
1 vanilla bean, split lengthwise
2 cups sugar
4 large egg whites
1/2 teaspoon salt
2 tablespoons coffee-flavored liqueur

Heat oven to 250 degrees F, with racks in upper and lower thirds.

Spread hazelnuts in a single layer on two rimmed baking sheets. Toast in oven, stirring halfway through, until fragrant and skins begin to crack, about 20 minutes. Remove from oven (leave oven on). While nuts are still hot, place in a kitchen towel; rub vigorously to remove skins. Let cool.

Scrape vanilla seeds into a small bowl. Stir in sugar; set aside.

Beat egg whites and salt in the bowl of an electric mixer until frothy. Pour in sugar mixture; whisk until thick and foamy. Whisk in liqueur; fold in nuts. Spread mixture on two baking sheets lined with nonstick Silpat baking mats.

Bake, stirring every 10 minutes, until nuts are golden, about 50 minutes. Let cool 10 minutes, then transfer to another baking sheet. Let cool 6 hours or overnight.

Nuts can be stored in airtight containers at room temperature up to five days.