How to Make It
Preheat oven to 325°F. Stir together 3 cups flour and salt in a medium bowl. Grease and flour a 10-inch (10- to 15-cup) Bundt pan. Set both aside.
Place sugar and butter in bowl of a stand mixer fitted with the paddle attachment; beat on high speed until light and fluffy, 5 to 6 minutes. Reduce speed to medium, and add eggs, 1 at a time, beating until fully incorporated after each addition and stopping to scrape down sides of bowl after every 2 eggs. With mixer running on low speed, add flour mixture in 3 additions alternately with heavy cream, beginning and ending with flour mixture. Stir in crème fraîche and vanilla.
Toss together chestnuts and remaining 2 tablespoons flour until well coated. Spoon half of batter into prepared pan; top with chestnuts. Add remaining batter, and smooth top. Tap cake pan on work surface to release any air bubbles. Bake in preheated oven until golden brown and a wooden pick inserted in center comes out clean, 1 hour to 1 hour and 20 minutes. Cool cake in pan on a wire rack 10 minutes. Invert cake onto wire rack, and let cool completely, about 2 hours.
To serve, transfer cake to a heatproof rimmed serving platter. Place Cognac in a heatproof measuring cup with a spout. Heat a small saucepan over medium until warm, about 30 seconds. Remove saucepan from heat, turn off burner, and pour in Cognac. Using a long match or lighter, carefully ignite fumes just above surface of Cognac. Slowly and carefully pour flaming liquid over cake. Allow flames to extinguish before slicing and serving.
Clement Faugier canned whole candied chestnuts can be purchased from amazon.com.