1. In a medium bowl, whisk together sour cream, hazelnut spread, and vanilla until evenly blended. Set aside. It's important that these ingredients be at room temperature and not cold.
2. Preheat oven to 350 degrees F. Spray a 9-inch tart pan with a removable bottom, a 9-inch springform pan, or a 9-inch pie pan with vegetable cooking spray.
3. Toast hazelnuts in a skillet and over medium heat, stirring frequently, until fragrant and lightly browned, about 5 minutes. Watch carefully to make sure they don't burn. Transfer to a small bowl. Reserve 1/4 cup nuts to use as a topping and add remaining 1/2 cup to a food processor.
4. Crumble cookies into food processor. Add butter and sugar and process until evenly blended. The mixture should look like wet sand. (Alternately, place cookies in a heavy-duty zip-close plastic bag and crush into fine crumbs using a rolling pin. Transfer to a bowl and mix with butter and sugar.) Firmly press crumb mixture into the bottom and up the sides of the tart or pie pan, or up 1 inch of the side of the springform pan if using. Bake for 10 minutes. Cool on a wire rack for 5 minutes, then refrigerate or freeze for faster cooling while you prepare filling.
5. Microwave chocolate in a large microwave- safe bowl on high for 30 seconds. Stir, then heat for 20 seconds at a time, stirring between each interval, until chocolate is evenly melted. Stir until smooth.
6. Add hazelnut spread-sour cream mixture to chocolate in three installments, whisking until smooth after each addition.
7. Pour filling into cooled tart shell. Spread it in an even layer. Sprinkle reserved hazelnuts over top and refrigerate for at least 6 hours and up to overnight.
8. Just before serving, prepare flavored whipped cream. In a large bowl, use an electric mixer on medium-high speed to whip cream, confectioners' sugar, and cornstarch until soft peaks form. Add coffee or liqueur and continue to whip until stiff peaks form.
9. Cut tart into wedges and serve with flavored whipped cream in a bowl on the side.
Source: Hannaford fresh Magazine, November - December 2013