In a medium bowl, whisk together flour, baking powder, cinnamon, nutmeg, salt, and espresso.
In the bowl of a stand mixer (or in a large bowl with a hand mixer), beat together pumpkin puree and ¼ cup sugar until smooth. Mix in vanilla.
Gently mix half of the dry ingredient mixture and half of the milk into pumpkin until just combined. Repeat with remaining dry ingredients and milk.
Lightly spray 4 8-ounce heat-proof mugs with cooking spray and fill about ¾ to the top with batter.
Place in microwave and bake for about one minute. Remove and let cool slightly.
Once mug cake has cooled a little bit, top with whipped cream and drizzle caramel sauce over the top. These mug cakes are best enjoyed hot, but whipped cream will melt if put on too quickly.