Carrot Mug Cake

Name: Carrot Mug Cake
Prep time: 3 min
Cook time: 2 min
Total time: 5 min
Cuisine: American
Ingredients: 1 ½ tablespoons vegetable oil; 1 large egg; ¼ cup shredded carrots (about 50g); 2 tablespoons milk; 1 tablespoon sugar; ¼ cup all-purpose flour; ¾ teaspoon ground cinnamon; ⅛ teaspoon ground nutmeg; ⅛ teaspoon ground allspice; 1 tablespoon chopped walnuts (optional); 1 batch cream cheese frosting