Prepare the Syrup: Combine 50ml water and 20g granulated sugar in a small saucepan. Heat until sugar dissolves. Set aside to cool.
Prepare the Sponge Cake Batter: Preheat your oven to 340°F (170°C). Grease and line an 8-inch round cake pan. Sift the cake flour.
Whip Egg Yolks: In a bowl, whisk the 4 egg yolks with the remaining 50g granulated sugar until pale and thick. Whisk in the vanilla extract.
Combine Wet Ingredients: Gently warm the milk and butter together until the butter melts. Whisk this mixture into the yolk mixture.
Whip Egg Whites: In a clean, grease-free bowl, beat the 4 egg whites until soft peaks form. Gradually add the 30g of remaining granulated sugar and continue beating until stiff, glossy peaks form.
Fold Together: Gently fold one-third of the meringue into the yolk mixture to lighten it. Sift the flour over the batter and gently fold until just combined. Fold in the remaining meringue in two additions, being careful not to deflate the air.
Bake: Pour the batter into the prepared pan. Bake for 25-30 minutes, or until a toothpick inserted comes out clean. Cool in the pan for 5 minutes, then invert onto a wire rack to cool completely.
Prepare Stabilizer: If using gelatin, sprinkle it over the 50ml cold water and let it bloom for 5 minutes. Gently heat the bloomed gelatin until fully dissolved, then let it cool slightly. If using Xanthan Gum, skip this step.
Make Whipped Cream: Chill your mixing bowl and whisk attachment. Pour the heavy cream into the bowl. Begin whipping on medium speed. Once soft peaks form, gradually add the powdered sugar. If using gelatin, slowly drizzle the cooled, dissolved gelatin into the cream while whipping until stiff peaks form. If using Xanthan Gum, sprinkle it in during the last minute of whipping.
Prepare Strawberries: Wash and hull the strawberries. Slice about two-thirds of them thinly for layering. Leave the remaining berries whole or halved for decoration.
Assemble the Cake: Once the cake is completely cool, slice it horizontally into two even layers. Place the bottom layer on your serving plate. Brush the cut surface generously with the cooled sugar syrup.
Layer: Spread a thin layer of whipped cream over the syrup. Arrange the sliced strawberries evenly over the cream. Top with the second cake layer. Brush the top layer with syrup.
Frost and Decorate: Cover the entire cake (top and sides) with the remaining whipped cream. Use an offset spatula for a smooth finish or a piping bag for decorative swirls. Arrange the reserved whole or halved strawberries on top. Chill for at least 1 hour before slicing and serving this fluffy strawberry cream cake.
Notes
For the lightest sponge cake, sift your cake flour twice before measuring and folding it into the batter gently.
If you prefer a less sweet flavor profile, reduce the powdered sugar in the cream to 20g.
For a perfect bakery look, use a turntable when frosting the sides of the cake.