Stir the cream and 1/3 cup of the sugar together in a large bowl. Beat the sweetened cream until soft peaks form. Set aside.
In a large bowl, using an electric mixer, beat the egg whites to soft peaks. Continue beating, adding the remaining 1/3 cup sugar 1 tablespoon at a time, until the whites form stiff, glossy peaks. Fold the cream mixture and beaten egg whites into the yogurt. Fold in the vanilla.
Line 1 large or 6 individual coeur a la creme molds or a large sieve with a double thickness of damp cheesecloth, allowing the excess to hang over the edge.
Fill the prepared mold(s) with the cream mixture and set over a large plate to drain. If using a sieve, set the sieve over a bowl. Fold the excess cheesecloth over the cream. Cover with plastic wrap and refrigerate for 24 hours.
Unwrap and invert the mold(s) onto a serving plate or plates. Remove the cheesecloth. Or, if using the sieve, invert onto a large plate and use an ice cream scoop to spoon individual servings into dessert bowls. Surround the coeur a la creme(s) with raspberry coulis and a few fresh raspberries.
In a medium bowl, using a wooden spoon, beat 8 ounces softened mascarpone cheese, 1/2 cup sugar, and 1 teaspoon pure vanilla extract together until smooth and creamy. In a large bowl, beat 1 cup heavy cream until it forms soft peaks. Fold the whipped cream into the mascarpone cheese mixture. Mold, drain, and serve as in the above recipe.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.
Courtesy of Simple French Desserts by Jill O'Connor (Chronicle Books, 2000)