Mix dry ingredients – In a mug, stir together flour, sugar, baking powder, cinnamon, nutmeg, ginger, cardamom, and salt until well combined.
Add wet ingredients – Add pumpkin puree, milk, oil, and vanilla extract. Stir gently until smooth. Small lumps are okay.
Microwave – Cook in the microwave on high for 70–90 seconds. Start with 70 seconds and check. The cake should spring back when lightly touched. Avoid overcooking.
Top and serve – Let it cool 1–2 minutes. Add whipped cream, chocolate chips, a sprinkle of cinnamon, or drizzle of caramel if desired. Enjoy straight from the mug.