To make the caramel sauce, combine sugar and water in a saucepan and cook until dissolved. Bring to a boil until deep golden copper, then add cream carefully and whisk until combined. Chill in fridge.

Preheat oven to 300°F. Prepare three 8-inch cake pans with parchment circles and grease sides.

Mix dry ingredients. Add eggs, milk, and oil. Incorporate boiling water and vanilla. Divide batter into pans and bake for 30-33 minutes. Cool completely.

Make buttercream: beat butter, add powdered sugar gradually, then add caramel sauce and salt to taste. Chill if needed.

Assemble the cake: level layers, spread frosting, add caramel and pecans between layers. Frost outer layer with remaining frosting.

Make ganache by heating cream and pouring over chocolate chips. Whisk until smooth. Drizzle over cake and pipe around edges.