Preheat the oven to 350⁰F/180⁰C. Spray baking pan with removable borders with cooking spray and line with parchment paper. Spray the paper with cooking spray.
Make the batter. Mix egg yolks and ½ cup of granulated sugar in a bowl of a stand mixer fitted with a whisk attachment on high speed until the foam is 3 times its original volume and falls in thick ribbons when the whisk is lifted. Transfer to a large mixing bowl, set aside.
Place egg whites in a clean bowl and beat them with a clean whisk attachment on medium speed until frothy. Gradually add the remaining ¼ cup of granulated sugar and continue to whip until medium peaks form when the whisk is lifted.
Fold the egg whites into the yolk mixture with a rubber spatula in 2 or 3 additions. Scatter all flour, vanilla, and salt over the batter and fold it just long enough to blend the flour evenly.
Bake. Pour the batter into the prepared pan and bakefor 30-35 minutes until the top is golden brown and the edges start to pull away from the sides of the pan. When finished baking, remove from the pan immediately, peel off the parchment paper, and let cool on a wire rack for 6-8 hours (otherwise the torte will not absorb the syrup properly and will become soggy). Cut the cake lengthwise to separate it into two disks.
Prepare the syrup. Pour water and sugar in a small sauce pan, bring to boil and turn off the heat immediately. Whisk so that the sugar completely dissolves. Let the syrup chill to about 37⁰C/98⁰F. Add the cognac and mix well. Apply the syrup evenly on each cake disk
Prepare the filling. Mix gelatin with the milk and let rest for about 1 hr. Bring the mixture to boil and immediately take off the heat. Gelatin should be completely dissolved. Chill the mixing bowl and whisk before making the cream. Pour cream into the bowl and mix on medium speed of a stand mixer until thickened. Gradually add confectioner’s sugar and whisk on high speed until the cream forms medium peaks. Pour the gelatin mixture over it to stabilize. Place one of the cake disks back into the baking pan, pour the filling over it, and cover with the second cake disk. Cover and refrigerate for the filling to set for about 2 hours.
Prepare the sauce according to the container instructions. Spoon it over the cake and sprinkle with walnuts. Keep the cake refrigerated before serving.