For crust, in a food processor combine gingersnaps and the 2 Tbsp. granulated sugar. Cover and process to form fine crumbs. With processor running, slowly add melted butter, processing until combined. Press mixture onto the bottom of a 9-inch springform pan. Chill until firm.
Place cream cheese in food processor. Cover and process until smooth. Add eggs, pumpkin, brown sugar, the 1/2 cup Frangelico, the cinnamon, vanilla, ginger, nutmeg, and cloves. Cover and process until smooth. Pour filling over crust, spreading evenly.
Place springform pan in a shallow baking pan. Bake in a preheated 350-degree oven for 40 to 45 minutes or until edge is firm and center appears nearly set when gently shaken.
Meanwhile, for topping, in a glass measuring cup combine sour cream, the 1/4 cup granulated sugar, and the 1/4 cup Frangelico. Carefully pour topping over cheesecake. Bake for 8 to 10 minutes more or until edge of topping just starts to bubble. Cool completely in pan on a wire rack. Cover loosely and chill for at least 12 hours.
To serve, loosen edge of cheesecake from side of pan; remove side of pan. Cut cheesecake while chilled. Let stand at room temperature for 20 minutes before serving. Sprinkle with hazelnuts.