With the rack in the middle position, preheat the oven to 350°F (180°C). Line two 8-inch (20 cm) springform pans with parchment paper. Butter and flour the sides.
In a bowl, combine the flour and baking soda. Set aside.
In a saucepan over medium heat, melt the butter with the beer and cocoa powder, stirring with a whisk. Let cool.
In a large bowl, combine the brown sugar, sugar and salt. With a whisk, add the lukewarm butter mixture alternately with the dry ingredients and eggs.
Add the sour cream and stir until the mixture is smooth.
Divide the batter among the pans and bake for about 50 minutes or until a toothpick inserted into the centre of each cake comes out clean. Unmould and let cool.
Place the chocolate in a bowl. Set aside.
In a saucepan, bring the beer, cream and syrup to a boil. Remove from the heat and pour over the chocolate. Let stand for 1 minute.
With a whisk, gently stir the mixture until the chocolate has completely melted. Add the butter and stir until smooth. Refrigerate for 1 hour or until the ganache is spreadable but not too thick. If needed, microwave a few seconds at a time and stir until spreadable.
Cut and discard the rounded tops of each cake. Spread one-quarter of the ganache onto one layer.
Top with the second cake layer and frost with the remaining ganache.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.