ESPRESSO HAZELNUT FUDGE

Steps:

• Line an 8-inch-square baking pan with aluminum foil that extends over the sides. Coat the foil with 1 tablespoon of the butter. Set aside.
• In a 3-quart heavy-bottomed saucepan over low heat, cook the espresso, sugar, cream, salt, cream of tartar, and the remaining 1 1/2 tablespoons butter until the sugar is dissolved (about 5 minutes), stirring constantly with a long-handled wooden spoon or heatproof spatula. Bring the mixture to a boil over medium heat, then brush down the sides of the pan with a pastry brush dipped in warm water to prevent the sugar from crystallizing. Place a sugar thermometer in the pan and cook the mixture without stirring until it registers 238°F on the thermometer (about 15 minutes).
• Remove the pan from the heat, remove the thermometer from the pan, and place the thermometer in warm water to cool. Sprinkle a marble board or the back of a baking sheet with cold water and immediately pour the hot mixture onto the marble. Do not scrape out the bottom of the pan. Let the mixture cool on the marble until it registers 110°F on the thermometer (about 5 minutes). If using a baking sheet instead of the marble, the cooling time will be about 15 minutes.
• Beat the fudge using one of the following three methods: With a 5-inch-wide flexible-blade scraper, transfer the mixture to the bowl of a stand mixer, add the ground cinnamon, and with the paddle attachment, beat the mixture until it thickens and loses its shine (5 to 10 minutes). Or transfer the mixture to a 2-quart mixing bowl, add the ground cinnamon, and beat the mixture with a long-handled wooden spoon until it thickens and loses its shine (10 to 15 minutes). In both cases, add the chopped hazelnuts after beating the fudge and mix until they are blended in (about 30 seconds). Or spread the mixture into a large rectangle on the marble board, sprinkle on the ground cinnamon, then use the 5-inch-wide flexible-blade scraper to gather the mixture back to the center of the marble, folding in the edges. Repeat this process until the mixture begins to thicken and lose its shine (5 to 10 minutes). Sprinkle on the chopped hazelnuts and continue to work the fudge to incorporate them (about 1 minute).
• Turn the fudge into the prepared pan. Use your fingertips to even the top and to press the fudge into the corners of the pan. Place the pan of fudge on a cooling rack and let it set completely at room temperature (1 to 2 hours).
• Remove the fudge from the pan by lifting out the aluminum foil. Invert the fudge onto a cutting board, peel the foil off the back of the fudge, and reinvert the fudge. With a large chef's knife, cut the fudge evenly into 1-inch squares. Between layers of waxed paper in a tightly covered container, the fudge will keep for 10 days at room temperature or 1 month in the refrigerator. The fudge is best served at room temperature.
• Espresso Almond Fudge: Substitute toasted, unblanched almonds for the hazelnuts.