To make the cake batter, stir the sugar and flour together in a bowl. Melt the butter on low in a saucepan, and when melted add the cocoa and Dr Pepper to the pan. Turn the heat to high and while stirring, heat until boiling. Turn off the heat.
While the cake is baking, to make the nuts, pour the ¼ cup Dr Pepper into a skillet, bring to a boil, then continue to cook on high until reduced in half to 2 tablespoons, about 3-5 minutes.
Turn the heat to low and add the butter. When melted, add the vanilla, then stir in the pecans until well coated. Stir in the sugar, cinnamon, salt, and clove, and while stirring, cook until the pecans are well coated and fragrant, about 3-5 minutes.
Remove from the skillet. Taste and adjust seasonings, if desired. (I usually sprinkle on a bit more cinnamon and sugar after cooking). These can also be made ahead of time and stored in an airtight container.
For the frosting, reserve 1/2 cup of the pecans as whole, then chop the remaining pecans.
Stir in the powdered sugar, vanilla, cinnamon, chopped pecans, and salt. Stir well until blended, then spread over the cake while both are still warm. Top the cake with the reserved whole pecans.
Dr Pepper sheet cake | www.homesicktexan.com