Preparation

Crust Preheat the oven to 375°F. Lightly brush vegetable oil over the bottom and sides of an 8-inch round fluted tart pan with 3/4-inch sides and a removable bottom. (Alternatively, spray the pan with non-stick cooking spray.) Use your fingers to thoroughly combine all of the crust ingredients in a small bowl, forming a loose, crumbly mixture. Press the crumbs firmly against the bottom and sides of the tart pan in a smooth, even layer. (For the most even coverage, form the sides first, pinching very firmly to press the crumbs into the pan's fluted edge. Use your fingers to gently pat the crumbs that remain into place, forming the bottom of the crust. Finish by using the base of a drinking glass or other flat implement to press the bottom of the crust firmly into place.) Bake the crust in the preheated oven for eight minutes. Allow to cool completely. Filling Chop the chocolate into small pieces and place it close at hand in a spacious, heat-tolerant bowl. Whisk the egg yolks and sugar together in a spacious bowl and set aside close at hand. Heat the cream in a small saucepan over medium heat until just barely simmering. Reduce heat to low. "Temper" the yolks by pouring in about 1/4 cup of the hot cream, whisking constantly to prevent the heat from curdling the yolks. Immediately transfer the tempered yolk mixture into the cooking pot, pouring in a thin, steady stream and whisking constantly. Cook over low heat, stirring gently but constantly, until the mixture thickens to the consistency of a rich cream sauce (this will take less than a minute). Immediately pour the hot mixture over the chopped chocolate. Allow to stand undisturbed for about a minute to melt the chocolate, then whisk gently until smooth. Whisk in the sour cream and the Chambord. Spread the raspberry preserves evenly over the bottom of the baked and cooled crust. Pour the chocolate filling over the preserves, smoothing if necessary with a small spatula. Chill the completed tart for at least four hours, or overnight. Just before serving, decorate as desired with fresh red raspberries.