For the truffles: Combine the chocolate, cream and butter in a small heatproof bowl set over simmering water and let melt. When almost melted, remove from heat and stir the mixture until smooth. Stir in your flavoring of choice and refrigerate until thick enough to mound on a spoon, stirring occasionally, about 30 minutes.
Line a baking tray with waxed or parchment paper. Scrape the chocolate mixture into a pastry bag fitted with a #3 plain tip. Pipe 8 (1-inch) mounds onto the prepared tray. Place 1 raspberry in the center of each chocolate mound and pipe a little more of the chocolate mixture to enclose completely. Refrigerate until firm, about 15 minutes.
For the cake: Position the rack in the center of the oven and preheat the oven to 350 degrees F. Butter or coat with vegetable spray, 8 oversize muffin cups (4-inches wide and 2-inches deep) or 1 1/4-cup custard cups. Line bottoms with rounds of waxed paper.
In the top of a double boiler or a small heatproof bowl set over simmering water, melt together the chocolate and butter, cool slightly.
Meanwhile in the bowl of an electric mixer with a paddle or beaters, beat the eggs, egg yolks and sugar on high speed until tripled in volume, about 5 minutes. Scrape in the chocolate mixture and, on low speed, beat until just combined. Remove the bowl from the mixer and fold in the flour, using a rubber spatula. Spoon a little of the batter into each of the prepared cups, top with 1 truffle, and cover with the remaining batter. Arrange the cups on a baking tray and bake until the edges of the cakes begin to pull away from the sides of the cups, 12 to 13 minutes.
Let stand 10 minutes. Invert onto individual dessert plates and carefully peel off the paper. Serve warm. Spoon softly whipped cream or ice cream next to each cake and, if desired, garnish with a few fresh raspberries. Serve immediately.
Recipe courtesy of Mary Bergin and Judy Gethers, Spago Desserts Random House, 1994.