If making the cake ahead of time, add the gelatin to the whipping cream – the final cake will set nicer. But if serving the cake right after you assemble, simply omit the gelatin without any worries.
Whip Cream Frosting
Preheat oven to 350 degrees F.
Line a 10-inch cake pan with parchment paper.
Sift cake flour onto parchment paper or into a bowl. Set aside.
In a large, stainless steel bowl whisk eggs, sugar, vanilla and salt by hand over a hot, barely simmering water bath until just warm to the touch (about 100 degrees F). Make sure the surface of the bowl is not touching the water or the eggs might start to cook.
Transfer egg mixture the bowl of a stand mixer fitted with whisk attachment (or alternatively with an electric hand mixer) beat on high speed for 4 to 6 minutes until tripled in volume and very pale yellow in colour.
With a slotted spoon, gently fold flour into egg mixture and immediately fold melted butter gently until blended.
Pour or scrape the batter into prepared pan and spread evenly with spatula if necessary. Bake for 20 to 25 minutes or until golden brown and firm to the touch. Cool on wire rack for 30 minutes before turning out. Cool on wire rack completely. Run knife along edge of cake to loosen it from sides of the pans. Invert the cake on another piece of parchment. To store wrap cake carefully in plastic wrap and store room temperature until ready to fill or serve.
In a small saucepan bring to a boil sugar, water and Grand Marnier. Let boil for 1 to 2 minutes. Remove from heat and let cool prior to brushing over cake.
In a medium heatproof bowl, sprinkle gelatin over 2 tbsp. of cream and let bloom for a few minutes. In a small saucepan bring ¼ cup of cream to a boil. Remove from heat. Slowly pour all of the heated cream into gelatin mixture, stirring constantly until gelatin dissolves, about 1 to 2 minutes. Let cool.
In the bowl of a stand mixer fitted with a whisk attachment (or alternatively with an electric hand mixer), set at medium speed, whip the 2 cups of cream with the sifted icing sugar. Slowly pour in the cooled gelatin mixture. Continue to whip cream, increasing speed to high, whipping to firm peaks. Use immediately to frost cake before the gelatin starts to set the whipping cream.
Slice the cooled cake in half. Brush the tops of both halves with simple syrup. Spread about 1/3 of the whipped cream frosting on the bottom layer of the cake. Place the sliced strawberries on top. Carefully place the top layer of cake and spread evenly with the remaining whipped cream frosting evenly over the top and sides of cake. Garnish top of cake with whole strawberries. Chill in the refrigerator for 30 minutes to 60 minutes to allow the whipped cream frosting to completely set. If desired, dust the top of the cake with icing sugar just prior to serving.