Preheat the oven to 375 degrees. Spray an 8-inch cake pan with oil. Cut a circle of parchment paper to line the bottom and spray paper as well.
Mix the milk with vinegar in a small bowl and set aside.
In a large bowl, mix the dry ingredients—flour through salt. Set aside.
Add the pumpkin, maple syrup, oil, vanilla, and espresso to the milk mixture.
Pour over top of the dry mix and mix well so that all of the dry mixture is incorporated. Fold in diced candied ginger.
Pour prepared cake batter into pan. Bake at 375 for 45 minutes, or until toothpick comes out clean.
Allow to cool 10 minutes on rack, and then remove from pan. Allow to cool completely on rack. Place on serving plate, with the baking bottom side up (you may need to trim the baking top with a large bread knife so that it sits flat, but I find that it usually squishes down just fine).