Preparation Steps

• Preheat the oven to 350°F (175°C). Grease a 13x18-inch sheet pan and set aside.
• In a large bowl whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt until evenly combined.
• In a separate bowl whisk buttermilk, vegetable oil, and eggs. Stir the wet ingredients into the dry ingredients until just combined.
• Slowly add the hot water to the batter, stirring until smooth. Pour the batter into the prepared sheet pan and smooth the top.
• Bake for 22 to 25 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Remove from oven and let cool in the pan for about 10 minutes.
• While the cake is still warm, prepare the caramel-pecan topping: In a medium saucepan melt butter over medium heat. Stir in brown sugar and sweetened condensed milk and cook, stirring constantly, until mixture is smooth and slightly thickened, about 3 to 4 minutes.
• Stir in the chopped pecans and vanilla extract. Immediately spread the caramel-pecan mixture evenly over the warm cake.
• Sprinkle the chocolate chips evenly over the hot caramel layer and let sit 2 minutes to soften. Pour the warm heavy cream over the chips and gently spread to form a smooth ganache.
• If desired, sprinkle a pinch of coarse sea salt over the ganache. Allow the cake to cool completely in the pan so the toppings set, about 1 hour, then slice into 24 squares.
• Store leftovers covered at room temperature for up to 2 days or refrigerate for up to 5 days. Serve at room temperature.