Instructions:
Preparing the Sponge Cake
Preheat the Oven:

Preheat your oven to 350°F (175°C). Grease and line a rectangular baking pan (approximately 9×13 inches) with parchment paper.
Prepare the Batter:

In a large mixing bowl, beat the egg whites with a pinch of salt until soft peaks form. Gradually add half of the sugar, beating until stiff peaks form.
In a separate bowl, beat the egg yolks with the remaining sugar until pale and fluffy. Add the vanilla extract.
Gently fold the beaten egg whites into the egg yolk mixture.
Sift together the flour and baking powder, then gently fold into the egg mixture, alternating with the milk until just combined.
Bake the Cake:

Pour the batter into the prepared baking pan, spreading it evenly.
Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool completely in the pan before cutting it into two equal layers.
Preparing the Custard
Make the Custard:
In a medium saucepan, heat the milk over medium heat until it begins to simmer.
In a bowl, whisk together the egg yolks, sugar, and cornstarch until smooth.
Gradually pour the hot milk into the egg mixture, whisking constantly to prevent curdling.
Return the mixture to the saucepan and cook over medium heat, stirring constantly, until the custard thickens and coats the back of a spoon.
Remove from heat and stir in the vanilla extract and butter. Allow the custard to cool slightly before using.
Assembling the Fruit Pavé
Prepare the Fruit:

Slice the strawberries, kiwis, mango, and any other desired fruits. Set aside a few slices for garnish.
Layer the Pavé:

Place one layer of the sponge cake in the bottom of a rectangular serving dish or a trifle dish.
Brush the cake layer with orange juice to moisten it.
Spread a generous layer of custard over the cake, followed by a layer of mixed fruit slices.
Repeat the layers with the second sponge cake layer, brushing with orange juice, spreading custard, and topping with fruits.
Final Touches:

Garnish the top layer with the reserved fruit slices, arranging them in an attractive pattern.
Chill the assembled pavé in the refrigerator for at least 2 hours, or overnight, to allow the flavors to meld.
Serving
Garnish and Serve:
Before serving, add a dollop of whipped cream and fresh mint leaves on top for an extra touch of elegance.
Slice the pavé into squares and serve chilled.
Tips for Success
Fresh Ingredients: Use the freshest fruits available to ensure vibrant flavors and a beautiful presentation.
Custard Consistency: Ensure the custard is thick enough to hold its shape between the layers. If it seems too thin, cook it a bit longer to thicken.
Chill Time: Allowing the pavé to chill for several hours or overnight enhances the flavor and texture, making it easier to slice.