Preheat oven to 350°. Prepare a Bundt pan by spraying with Baker's Joy, or similar product.
Combine the cake mix, pudding, eggs, water, oil and extract in a large mixing bowl. Beat with an electric mixer on low just to blend, then turn to medium and beat for 2 minutes, scraping the sides of the bowl as you go.
Pour one cup of the batter into a separate bowl and stir in the chocolate syrup and unsweetened cocoa. Mix well so unsweetened cocoa powder is well incorporated!
Evenly pour about 1-1/2 to 2 cups of the "green" batter into the prepared Bundt pan. Spoon 1/3 of the chocolate batter over the green batter, staying in the center, away from the sides of Bundt. Cover chocolate batter with more green batter, spoon on more chocolate batter, etc., until both batters are used. Using a metal long spatula or dull knife, GENTLY zig-zag a pattern through the batters to make the marble effect. Be careful not to drag spatula across bottom or sides of pan, so as not to scrape off the Baker's Joy coating.
Bake for approximately 50 - 58 minutes if using a Bundt pan. Use a cake tester right at 50 mins ...your oven might not require any more time. I also use a stoneware Bundt pan, which can make a difference. If making this in a 13x9 or other pan, you'll have to use your judgment and rely on your ol' cake tester for doneness.
Cool for 15 minutes before removing from pan, then cool completely on a wire rack.
Top with your favorite fudge or chocolate frosting, or with pistachio frosting [below], or simply sprinkle with powdered sugar, once completely cooled.
For the pistachio frosting, make sure your cream cheese is very soft. Mix the pkg. of pistachio pudding mix, powdered sugar, soft cream cheese and just enough milk to make a spreading consistency; start with a TBSP or two of milk, and add only a little bit at a time, if necessary. Mix well, so no lumps are left behind by the cream cheese. I use my electric mixer for this, once all ingredients are incorporated and moistened.
Apply frosting to COOLED cake.