If starting with a pumpkin:
1. Fill a large pot of water with about 2 inches of water and bring to a boil. Place a colander on top of the pot so it is just above but not touching the water. Add pumpkin pieces, cover, and steam for about 10-15 minutes, until pumpkin is soft. Remove from heat and puree in a food processor until smooth. Let cool, then transfer to refrigerator.
To make custard base:
1. Heat whole milk in a small saucepan over medium heat until just barely boiling. Remove from heat, add grated ginger and cover. Let cool, then steep for at least three hours or up to overnight in refrigerator.
2. Strain out ginger from milk. Heat milk over medium low heat until warm.
3. Meanwhile, using a stand mixer, beat eggs, sugar, powdered ginger, nutmeg, cloves, and salt until it thickens and starts to turn white, about 3 minutes. Gradually beat in warm milk.
4. Pour mixture back into saucepan and return to stovetop. Stirring constantly, cook over medium low heat, until mixture thickens enough to coat the back of a spoon, about 8-10 minutes. Remove from heat and let chill completely. Once chilled, add 1½ cups pureed pumpkin and heavy cream.
To make ice cream:
1. Churn ice cream based on your ice cream maker manufacturer’s instructions. Eat right away, or freeze overnight for firmer ice cream.