Combine the granulated sugar and water in a medium to large saucier pan. Cook over medium-low heat until the sugar is completely dissolved, about 3 to 5 minutes. Add the butter and let it melt.

Over medium heat, bring the mixture to a boil. Stop whisking and don’t whisk at all during this part to help avoid crystallization. Allow to boil until the mixture turns a deep golden copper color, about 15-20 minutes. Keep an eye on it but do not stir.

Remove the pan from the heat and immediately add in the heavy whipping cream in a slow, steady stream. Whisk quickly until well combined.

Add the vanilla extract and half a teaspoon of salt and whisk to combine; adjust salt according to taste. Set the caramel sauce in the fridge to cool.

Prepare three 8-inch cake pans with parchment paper circles in the bottom and grease the sides. Preheat oven to 300°F (148°C). In a large bowl, add all dry ingredients and whisk together.

Add eggs, milk and vegetable oil to the dry ingredients and mix well before adding boiling water along with vanilla extract; mix again until well combined. Divide batter evenly between cakes pans and bake for approximately 30–33 minutes or until a toothpick comes out with just a few crumbs attached.

Remove cakes from oven allowing them to cool for about ten minutes before transferring them onto cooling racks to cool completely.

While cakes are cooling, prepare the buttercream by adding butter into a large mixer bowl; beat until smooth before gradually adding half of the powdered sugar while mixing until combined well.

Incorporate about half a cup of cooled caramel sauce mixing until smooth before adding remaining powdered sugar while continuing to blend until fully combined.

Adjust frosting consistency by adding additional caramel sauce for flavor without thinning out too much; season with salt according to taste.

Once cakes have cooled down completely and frosting is ready, remove domes from tops using serrated knife for leveling purposes.

Place first layer of cake on cake plate spreading approximately two-thirds of a cup of frosting evenly across top surface followed by piping a dam around edges.

Gently spread half a cup of cooled caramel sauce over frosted layer followed by sprinkling one-quarter cup toasted pecans evenly across surface before placing second layer over top repeating frosting/caramel layering process once more before finally adding last layer atop everything else.

Chill assembled cake in refrigerator for thirty minutes up to an hour allowing firming action take place. Frost entire outside area using remaining whipped frosting.

Begin by creating chocolate ganache involving melting semi-sweet chocolate chips together heating cream until boiling then pouring over chips allowing resting period followed by mixing into silky texture.

Drizzle ganache generously around edges cascading down gently while topping off center surface achieving visual appeal.