Preheat the oven to 350°F (175°C). Grease and flour your cake pans, or line with parchment paper.
In a medium bowl, whisk together flour, cocoa powder, baking powder, and salt. Set aside.
In a separate large bowl, use a hand mixer or stand mixer to cream together butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Gradually add the dry ingredients, alternating with milk, beginning and ending with the flour mixture. Mix until just combined.
Divide the batter evenly between the two prepared pans and smooth the tops.
Bake for 25-30 minutes, or until a toothpick inserted comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer to a cooling rack to cool completely.
While the cakes cool, make the chocolate filling: In a small saucepan, heat the heavy cream over medium heat until it starts to simmer. Remove from heat and stir in the chocolate chips until melted and smooth.
Once the cakes are cool, place one layer on a serving platter. Spread the chocolate filling over the top, then place the second cake layer on top. The filling will ooze out when you cut into it—creating a “chocolate eruption.”
Dust with powdered sugar, if desired, and serve! Enjoy the rich and gooey chocolate goodness.