With the rack in the middle position, preheat the oven to 180 °C (350 °F).
Line a 43 x 30-cm (17 X 12-inch) baking sheet with parchment paper, letting it hang over two sides. Butter and flour the baking sheet.
In a bowl, combine the flour, ground almonds, baking powder, and salt. Set aside.
In another bowl, beat the egg whites with the cream of tartar until soft peaks form. Gradually add half the sugar and beat until stiff peaks form. Set aside.
In another bowl, beat the whole eggs, remaining sugar, and vanilla with an electric mixer until light and fluffy, triples in volume, and forms a ribbon falling off the beaters, about 10 minutes. With a spatula or a whisk, gently fold in the dry ingredients and melted butter. Fold in the meringue. Spread the batter on the baking sheet. Bake for about 12 minutes or until the cake is lightly golden brown. Cool completely.
Place the egg yolks in a large bowl. Set aside.
In a saucepan, bring the water, sugar, and corn syrup to a boil. Simmer until a candy thermometer reads 106 °C (224 °F), about 3 minutes.
Beat the eggs with an electric mixer at medium speed until light and fluffy. Drizzle the hot syrup over the eggs, avoiding the beaters of the mixer. Beat until completely cooled, about 15 minutes.
Add the butter, one or two pieces at a time, beating until very smooth.
In a small bowl, combine the coffee and water. Let cool.
Divide the buttercream into three bowls. In the first bowl, stir in the vanilla. In the second bowl, stir in the chocolate. In the third bowl, stir in the coffee. Set aside.
In a bowl, combine the coffee and sugar. Set aside.
In a bowl, combine the chocolate and cream until the chocolate is melted and smooth. Let cool.
On a work surface, cut the cake into three 30 X 13-cm (12 X 5 ½-inch) strips.
Place the first strip on a rectangular service plate. With a brush, soak the first cake layer with syrup. Spread the chocolate buttercream over the whole surface. Layer with a second cake strip, brush with syrup, and cover with the coffee buttercream. Continue with the third cake strip. Brush with syrup and cover with the vanilla buttercream and smooth the surface with a spatula. Refrigerate for 30 minutes. If desired, trim the edges for an even cake. Cover the top of the cake with lukewarm ganache.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.