Start by preheating your oven to 350°F and preparing a 12-cup bundt pan by greasing and flouring it thoroughly.
Mix the strawberry cake according to the package directions, combining the 1 (18 ounce) package strawberry cake mix with 3 eggs, 1/3 cup oil, and 1 1/3 cups water (or whatever amounts your specific cake mix calls for).
Once your batter is smooth and well-combined, pour about three-quarters of it into your prepared bundt pan, spreading it evenly across the bottom.
To create the marble effect, melt the 1/2 cup semi-sweet chocolate chips and stir them thoroughly into the remaining strawberry batter in your mixing bowl.
Carefully spoon this chocolate-strawberry mixture in a narrow ring on top of the plain batter already in the pan, making sure to keep the chocolate batter away from the edges of the pan. This technique will create beautiful marble swirls throughout the cake as it bakes.
Bake according to your cake mix's specific directions, typically 35-40 minutes, until a toothpick inserted in the center comes out clean.
Allow the cake to cool in the pan for 10-15 minutes before turning it out onto a wire rack to finish cooling completely. Once cooled, warm the 1 (15 ounce) container chocolate frosting in the microwave for about 15 seconds to create a pourable glaze consistency, then drizzle it over the top of the cake.
You'll likely only need about half the container for proper coverage, so save the remainder for future use or apply more generously if you prefer extra frosting.