Preheat oven to 350°F (175°C). Grease and line two 8- or 9-inch round cake pans with parchment. Whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt in a large bowl until evenly combined.

In a separate bowl, whisk eggs, milk, vegetable oil and vanilla until combined. Add wet ingredients to dry and mix until just combined. Gradually add the hot water while stirring (batter will be thin).

Divide batter evenly between prepared pans and bake 25–30 minutes, or until a toothpick inserted into the center comes out with moist crumbs. Cool in pans 10 minutes, then turn out onto a wire rack to cool completely. If desired, level the domes with a serrated knife so layers are flat.

Milk Chocolate Ganache Cream

Make Ganache

Chop the milk chocolate and place in a heatproof bowl. Heat heavy cream in a small saucepan until it just begins to simmer; do not boil. Pour hot cream over chopped chocolate and let sit 1 minute to soften.

Stir gently until smooth. Add butter and salt and stir until fully incorporated and glossy. Let ganache cool to lukewarm, then refrigerate briefly (10–15 minutes) until it thickens to a spreadable but still pipeable consistency. Stir once or twice while cooling to maintain even texture.

Condensed Milk Cream

Prepare Cream

Place chilled heavy cream in a chilled mixing bowl and whip to medium peaks. In another bowl, beat mascarpone (or cream cheese) until smooth. Gradually fold the sweetened condensed milk and powdered sugar into the mascarpone until smooth and homogenous, then fold in vanilla.

Gently fold the whipped cream into the condensed milk-mascarpone mixture a third at a time until fully combined and light. Refrigerate until assembly.

Strawberry Filling & Decoration

Macerate Strawberries

Combine sliced strawberries, 2 tablespoons granulated sugar and lemon juice in a bowl. Toss gently and let sit at room temperature 15–20 minutes to macerate and release juices. Drain most of the liquid (reserve a little for brushing cake layers or mixing into condensed cream if desired).

Hull whole strawberries reserved for decoration and pat dry. Leave some whole for tops and slice a few for edge decoration.

Assembly & Finish

Optional Simple Syrup

If using simple syrup, warm equal parts sugar and water (to make 1/2 cup) until sugar dissolves. Cool. Brush a light coat on each cake layer to keep them moist.

Layer the Gateaux

Place the first cake layer on a cake board or plate. Spread about half of the condensed milk cream over the layer to an even thickness (reserve the rest for top/filling). Arrange half of the macerated strawberry slices over the cream. Pipe or spread a thin ring of ganache cream around the strawberry edge if you want a chocolate barrier (optional). Place the second cake layer on top and press down gently.

Spread the milk chocolate ganache across the top and slightly down the sides for a thin crumb coat. Refrigerate 15 minutes to set the ganache slightly.

Apply the remaining condensed milk cream to the top and sides, smoothing with an offset spatula. Use remaining strawberry slices between layers if you created more layers or to decorate between top cream and sides.

Decorate

Decorate the top with whole strawberries, chocolate shavings and a light dusting of cocoa powder. If you like a glossy finish, warm a few tablespoons of ganache and drizzle thin ribbons over the top strawberries. Chill the assembled gateaux at least 1 hour to firm before serving; bring to room temperature 15–20 minutes before slicing for best texture.