Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans. In a large bowl, whisk together the all-purpose flour, cocoa powder, sugar, baking powder, and salt until combined. In another bowl, blend the eggs, vegetable oil, milk, and vanilla extract. Gradually mix the wet ingredients into the dry until just incorporated. Divide the batter evenly between the prepared pans and bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.

While the cake layers are cooling, start on the Earl Grey buttercream. In a small saucepan, heat the heavy cream until steaming, then steep the Earl Grey tea for about 15 minutes. Remove the tea leaves and let the cream cool. In a medium bowl, beat the unsalted butter until creamy and light, about 5 minutes. Gradually add the sifted powdered sugar and cooled cream, mixing on low until fluffy and well combined.

Next, focus on the indulgent salted caramel sauce. In a medium saucepan over medium heat, cook the granulated sugar, stirring constantly until it melts and turns a golden amber color, about 8-10 minutes. Carefully add the cubed butter and warm heavy cream, stirring until smooth. Remove from heat and stir in sea salt to taste. Let the caramel cool slightly to thicken before drizzling.

Once the chocolate cake layers are completely cool, level them using a serrated knife if necessary. Place one layer on a serving plate and spread a generous amount of Earl Grey buttercream on top. Carefully place the second cake layer on top and frost the entire cake with the remaining buttercream, smoothing the sides and top for an elegant finish. Finish by drizzling the salted caramel sauce over the cake, allowing it to cascade down the edges.

For the best flavor and texture, let the assembled London Fog Cake sit at room temperature for about 30 minutes before slicing. This allows the buttercream and caramel to soften perfectly. Cut into slices and serve with a cup of tea or coffee for a delightful pair with this decadent treat.