These melt-in-your-mouth cinnamon rolls have a secret ingredient: vanilla cake mix.
In a large mixing bowl, combine the dry cake mix, 2 cups of the flour, the yeast, and salt. Add the water and beat with an electric mixer on low speed until combined, scraping sides of bowl. Beat on high speed for 3 minutes.
Stir in as much remaining flour as you can with a wooden spoon. Turn dough out onto a floured surface. Knead in enough of the remaining flour to make a smooth dough (about 3 minutes; dough will still be slightly sticky). Place dough in a large greased bowl. Cover and let rise in a warm place until doubled in size (about 1 hour).
Punch dough down. Turn dough out onto a well-floured surface and divide in half. Cover and let stand for 10 minutes. Roll each portion to form a 16x9-inch rectangle.
Spread each rectangle with half of the 1/4 cup butter. Sprinkle with a mixture of granulated sugar and cinnamon. Starting from a long side, roll up dough into a spiral. Pinch to seal. Cut the dough into 1-inch slices.
In a saucepan, combine the brown sugar, the 1 cup butter, and corn syrup. Bring to boiling. Remove from heat. Divide mixture between two 13x9x2-inch baking pans.
Sprinkle walnuts evenly into the pan. Place half of the rolls, cut side down, into each baking pan. Cover and refrigerate for 8 hours or overnight.
Before baking, remove from refrigerator and let stand at room temperature for 30 minutes. Bake in a 350 degree F oven about 25 minutes or until golden. Let cool for 10 minutes in pans on wire racks. Turn out onto foil. Serve warm or cool. Cover and store at room temperature for 8 hours or wrap and freeze for up to 3 months.