Chocolate Sheet Cake with Milk Chocolate Ganache Frosting

Ingredients

• For the Cake:
• 1 1/4 cups (6 1/4 oz) all-purpose flour
• 3/4 cup (2 1/4 oz) Dutch-processed cocoa powder
• 2 teaspoons instant espresso powder
• 1/4 tsp salt
• 8 ounces semisweet chocolate, chopped (I used chips)
• 12 tablespoons unsalted butter
• 4 large eggs, at room temperature
• 1 1/2 cups (10 1/2 oz) granulated sugar
• 1 teaspoon vanilla extract
• 1 cup buttermilk
• 1/2 teaspoon baking soda
• 16 ounces milk chocolate, chopped (or high quality chips)
• 16 ounces heavy cream
• Flaky sea salt for tasting