Pour the mixture evenly into the prepared bundt pan. Bake for about 1 hour. The exact time will depend on the type of pan you have. Test the cake with a toothpick or an internal thermometer. The cake should be about 200º Fahrenheit.
Cool on a wire rack on the counter for 15 minutes in the pan. Turn out onto the wire rack to cool completely.
To make the icing, combine the powdered sugar and cinnamon in a small bowl. Add 3 tablespoons of heavy cream. Mix until it is smooth. Add more heavy cream, one tablespoon at a time, until the glaze is thin enough to spread or drizzle. Drizzle the cinnamon icing on the bundt cake. Sprinkle with walnuts if you'd like.
Measure your mashed sweet potatoes packed and level, not heaped. Too much and the center bakes up wet and gummy. You want a full 3½ cups, smoothed into the measuring cup.You can use canned sweet potatoes if you’d like. Use a 30 ounce can and drain off any liquid.Store in an airtight container at room temperature.The calories shown are based on the cake being cut into 12 pieces, with 1 serving being 1 slice of cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information. The information in the nutrition box are calculated through a program and there is room for error. If you need an accurate count, I recommend running the ingredients through your favorite nutrition calculator.**