Preheat oven to 350 degrees F.
Butter and flour two 9-inch round cake pans.
In a standing mixer, cream butter and sugars together until fluffy in a standing mixer.
Beat in eggs and vanilla.
Put the water, chocolate, and espresso powder in a small saucepan and stir on low heat until melted. Allow to cool slightly and then beat into butter mixture.
Sift together flour, baking soda, and salt and stir into batter alternately with sour cream.
Divide batter evenly between the 2 pans and bake for 25 minutes, until a tester inserted in the centre of the cake comes out clean.
Allow to cool for 15 minutes in the pans, then turn cakes out onto a plate or rack to cool completely.
In a medium pot, whisk together cornstarch, cream, corn syrup, sugars, and egg yolks.
Cut up butter into small pieces and add to pot.
Over medium heat, whisk goopy topping constantly until bubbly and shiny, about 4-5 minutes.
Remove from heat and immediately scrape out topping into a bowl, to halt the cooking process.
Stir in vanilla, salt, pecans, and coconut.
Cover and chill completely.
Melt chocolate in a bowl over a pot of simmering water or in the microwave at medium heat, stirring every 20 seconds. Set aside. Let cool slightly.
Beat egg whites with cream of tartar until stiff peaks.
Bring water and sugar to a boil and cook over high heat until temperature reaches 240 degrees F (softball stage). You can use a candy thermometer, or test by spooning a little of the hot sugar syrup into a glass of ice water – if you can roll it between your fingers into a soft ball, then it is ready
While beating whites at medium speed, slowly add sugar syrup (be careful – it’s hot!) until all the syrup has been added. Continue to beat whites until cool, about 3 to 4 minutes.
Start adding butter to egg whites, a little at a time, while mixing constantly and scraping the sides of the bowl often, until all the butter has been incorporated. If the frosting looks like it’s separating or looks curdled, don’t worry – just keep mixing and it will come together.
Mix in melted chocolate, vanilla, cocoa powder and salt. Keep at room temperature to ice cake. If making a day ahead, chill frosting but bring to room temperature and beat well before using.
Level cakes if necessary, using a serrated knife. Spread a dollop of chocolate frosting on one layer of cake. Spoon a third of the goopy topping over frosting. Spread in the centre of the cake leaving an inch from the edge of the cake, without topping.
Place second cake on top of first and dollop a generous amount of chocolate frosting on top. Spread to edges of cake, working from the middle and turning the cake as you work around. Ice the sides of the cake, but leave about ½ cup of icing for piping, if desired.
Spread remaining goopy topping on top of cake, leaving ½ inch around the outside edge. If you do not wish to pipe outside edge with chocolate frosting, simply garnish the cake with toasted pecan halves.
To pipe an edge, place frosting in a piping bag fitted with a star tip or leaf tip. Pipe frosting as desired. Remember – it’s just frosting! If you’re not pleased with how it looks, just scrape it off and start again. Again remember to lick your fingers often!
Cake can be chilled until ready to serve. Frosting will firm up once chilled.