Prepare the Chocolate Cake:

1. Preheat Oven: Preheat your oven to 350°F (180°C). Grease a 9 x 13-inch (23 x 33 cm) baking pan and line it with parchment paper, leaving an overhang on two sides.
2. Mix Wet Ingredients: In a large mixing bowl, beat the butter, granulated sugar, and brown sugar together with an electric mixer on medium speed until light and fluffy.
3. Add Eggs and Vanilla: Add the vanilla extract and eggs one at a time, beating well after each addition.
4. Combine Dry Ingredients: In a separate bowl, sift together the all-purpose flour, cocoa powder, baking powder, baking soda, and salt.
5. Mix the Batter: Gradually add the dry ingredients to the wet mixture, alternating with the hot water, mixing on low speed until just combined.
6. Add Sour Cream: Gently fold in the sour cream until the batter is smooth.
7. Bake: Pour the batter into the prepared pan, smoothing the top with a spatula. Bake for 35 minutes or until a toothpick inserted into the center comes out clean.
8. Cool: Allow the cake to cool in the pan for 15 minutes, then transfer it to a wire rack to cool completely.

Prepare the Chocolate Crumbs:

1. Preheat Oven: Preheat your oven to 350°F (180°C) if not already heated.
2. Combine Ingredients: In a mixing bowl, whisk together the all-purpose flour, granulated sugar, cornstarch, and cocoa powder.
3. Add Butter: Pour in the melted butter and stir until the mixture forms small, moist crumbs.
4. Bake: Spread the crumbs evenly on a lined baking sheet. Bake for 10 minutes, then allow them to cool completely.

Prepare the Cherry Syrup:

1. Combine Ingredients: In a saucepan, whisk together the reserved cherry syrup, granulated sugar, and cornstarch until smooth.
2. Cook: Place the saucepan over medium heat and bring the mixture to a gentle boil, stirring constantly until it thickens, about 3–4 minutes.
3. Cool: Remove from heat and let the cherry syrup cool completely.

Whip the Cream:

1. Beat Cream: In a large chilled bowl, beat the heavy whipping cream on low speed for 1 minute using an electric mixer.
2. Add Vanilla: Add the vanilla extract and continue beating on medium speed until soft peaks form. Be careful not to overwhip.

Assemble the Cake:

1. Cut Cake Layers: Using a 6-inch cake ring, cut out two full circles and two half circles from the cooled cake.
2. Prepare Cake Ring: Place the cake ring on a serving plate and line the inside with an acetate sheet or parchment paper for support.
3. First Layer:
   • Place the two half circles inside the ring to form a complete layer.
   • Brush the layer with 3 tablespoons of the cherry syrup.
   • Spread a layer of whipped cream over the cake.
   • Sprinkle with some cherries and chocolate crumbs.
4. Second Layer:
   • Add one of the full cake circles on top.
   • Repeat the layering of cherry syrup, whipped cream, cherries, and chocolate crumbs.
5. Top Layer:
   • Place the final cake circle on top.
   • Finish with the remaining whipped cream, cherries, and chocolate crumbs.
6. Chill: Refrigerate the assembled cake for at least 2 hours to set.
7. Serve: Gently remove the cake ring and acetate. Slice and enjoy your Chocolate Cherry Cake!