01 -
Preheat oven to 350°F. Grease a 9x13-inch baking dish with unsalted butter.
02 -
Combine melted butter, whole milk, instant espresso powder (if using), and kosher salt in the prepared baking dish. Stir to dissolve the espresso powder.
03 -
Evenly sprinkle chocolate cake mix, instant chocolate pudding mix, and 1 1/4 cups semisweet chocolate chips over the liquid mixture. Gently stir until just incorporated.
04 -
Smooth the surface into an even layer. Distribute remaining 1/2 cup semisweet chocolate chips over the top.
05 -
Transfer baking dish to the oven and bake for 35 to 40 minutes, until the cake is barely set and a toothpick inserted in the center comes out with moist crumbs attached.
06 -
Let cool for about 5 minutes before serving. Enjoy warm with vanilla ice cream or whipped cream if desired.