In a medium saucepan, combine granulated sugar and water over medium heat. Stir gently until sugar dissolves, then stop stirring. Allow the mixture to cook undisturbed until it turns a deep amber color, approximately 8-10 minutes. Remove from heat, and carefully whisk in unsalted butter, heavy cream, vanilla extract, and a pinch of salt. Let the caramel cool to room temperature while you tackle the cake batter.

In a large mixing bowl, sift together the all-purpose flour, unsweetened cocoa powder, baking soda, baking powder, and granulated sugar. In another bowl, mix the eggs, milk, vegetable oil, and vanilla extract until well combined. Pour the wet mixture into the dry ingredients and mix until just combined. Slowly add the boiling water, and stir until the batter is smooth and glossy.

Preheat your oven to 350°F (177°C) and prepare two 9-inch round cake pans by greasing them with butter and dusting with flour. Divide the chocolate batter evenly between the pans. Bake for 30-33 minutes, or until a toothpick inserted comes out clean. Allow the cakes to cool in their pans for about 10 minutes before transferring them to wire racks to cool completely.

In a mixing bowl, beat unsalted butter until light and fluffy, about 2-3 minutes. Gradually add the powdered sugar, mixing on low speed until incorporated. Slowly pour in the cooled caramel sauce and continue beating until the frosting is smooth and creamy.

In a small saucepan, heat the heavy cream over medium heat until simmering. Remove it from heat and pour it over the semi-sweet chocolate chips in a bowl. Allow it to sit for a minute, then stir until the chocolate melts completely.

Once the chocolate cake layers are completely cooled, place one layer on a serving plate. Spread a generous layer of caramel frosting over the top, followed by a sprinkle of chopped pecans. Carefully place the second cake layer on top and repeat the process before drizzling the ganache over the top.

Slice the Turtle Chocolate Layer Cake using a warm knife and serve it. Store any leftovers in an airtight container at room temperature for up to a week.