My grandma's Texas sheet cake recipe makes a moist chocolate cake topped with fudgy frosting. This recipe takes just 30 minutes total to make from scratch.
Greek yogurt or sour cream: If using Greek yogurt, fat-free, 2% or full-fat Greek yogurt is ok. For sour cream, I recommend using full-fat. You can also sub an equal amount of buttermilk in place of the Greek yogurt.
Icing: The frosting should be on the thicker side. Add additional powdered sugar as needed.