Place coarsely chopped Roasted Chestnuts in a small bowl, sprinkle Rum over, and set aside.
Preheat oven to 170°C. Grease a loaf tin and line the base and sides with baking paper.
Beat the softened Butter in a mixing bowl with a whisk or an electric mixer until smooth. Add Sugar and Sweetened Chestnut Paste, and beat until creamy.
Add Eggs, one at a time, beating well after each addition. If the Eggs are not warm enough, the mixture will curdle. If that happens, try to stand the bowl in warm water, stirring constantly, for 30 seconds, then continue beating until the batter becomes smooth and creamy.
Add Vanilla Extract, and gently fold in Flour with a spatula or large metal spoon until just combined. Add Chestnuts and Rum, and combine evenly.
Spoon the mixture into the loaf tin and smooth the surface. *Note: I spread the middle part thinner and the edges thicker.
Bake in preheated oven for 40 to 45 minutes or until cooked through. Stand the cake in the tin for 5 minutes as it is very soft, then turn onto a wire rack to cool.
