Preheat your oven to 350°F. Lightly grease the bottom and sides of a 12x16-inch or 10x15-inch rimmed baking sheet with cooking spray or melted butter and line it with parchment paper. Lightly spray the parchment with cooking spray also.
For the sponge cake, beat eggs for 3 minutes on medium-high speed until frothy and pale in the bowl of an electric stand mixer fitted with the whisk attachment or in a large mixing bowl if using an electric hand mixer. Gradually add sugar and beat for 4-5 minutes longer, until it nearly triples in volume and is very thick, pale and fluffy and billowy like shaving cream or marshmallow fluff. When you lift the mixture up with the beater and it slides back down into the base mixture, it should fall back onto itself in folds or ribbons rather than sink down into it. Mix in vanilla and salt, then mix in oil just until it is evenly blended.
Sift flour, cocoa, espresso powder and baking powder into a medium bowl and whisk to blend evenly. Sift it again over the bowl with the egg mixture and use a large rubber spatula to carefully fold the dry ingredients into the whipped egg mixture just until combined without over-mixing.
Spread batter evenly into prepared pan in a thin layer. Bake for 9-11 minutes until it springs back when pressed gently. Transfer pan to a wire rack and let cool completely.
Run a knife along the edges of the pan to release the cake, then invert it onto a clean surface or a large piece of parchment paper. Gently peel off the parchment from the cake and then slice it into 3 equal rectangles.
For the filling, place ¼ cup (60ml) whipping cream and espresso in a small saucepan over medium-low heat until it just comes to a simmer. Remove from heat and add finely chopped dark chocolate. Let stand for 1 minute then whisk until smooth and glossy. Pour it into a clean bowl and let cool for 10 minutes, then gently fold in the whipped cream.
Place on sponge layer onto a lined tray or baking sheet so it is easy to transfer. Spread half of the filling evenly over this bottom sponge rectangle, place another rectangle on top and then spread the remaining filling over it. Place the last sponge layer on top and then smooth out the sides to even out any filling that squeezes out. Refrigerate for 15 minutes.
To make the chocolate glaze, place chopped chocolate in a medium bowl. Heat cream with honey in a small saucepan until it just comes to a simmer. Pour it over the chopped chocolate and whisk gently until smooth and glossy. Immediately pour it over the chilled cake and quickly spread it out to cover the top and sides evenly. Place it back in the fridge to set for 1-2 hours before serving. Top with sprinkles and ruby chocolate curls and enjoy!