Preheat your oven to 350°F (175°C) and grease and flour two 9-inch cake pans.

In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

In a separate large bowl, beat the butter and sugar together until light and fluffy, about 3 minutes.

Add the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract.

Gradually add the dry ingredients into the wet mixture, alternating with the milk. Start and finish with the flour mixture. Mix until just combined—don’t overmix.

Pour the batter evenly into the prepared pans and bake for 25–30 minutes, or until a toothpick inserted into the center comes out clean.

Let the cakes cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.

While the cake is cooling, it's time to make the creamy filling. In a medium saucepan, heat the milk over medium heat until just simmering. Keep an eye on it, but don’t let it boil.

In a separate bowl, whisk together the sugar, egg yolks, and cornstarch until smooth.

Slowly 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 it thickens and starts to bubble—about 5-7 minutes.

Once thickened, remove from heat and stir in the butter and vanilla extract. Let the pastry cream cool to room temperature, then refrigerate until ready to assemble.

In a heatproof bowl, chop the semi-sweet chocolate into small pieces.

In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer.

Pour the hot cream over the chopped chocolate and let it sit for 2-3 minutes. Then stir until the chocolate is fully melted and the ganache is smooth. If you want extra shine, add butter for a glossy finish.

Let the ganache cool slightly, but not too much—you want it pourable, not set.

Once the cakes have cooled, place one layer on a serving plate. Spread the chilled pastry cream evenly on top.

Place the second cake layer on top of the cream, gently pressing down to secure it.

Pour the chocolate ganache over the top, letting it drip down the sides for that gorgeous, rustic look.