In a large bowl, mix all of the dry ingredients together.
In a smaller bowl, beat together the egg, milk, and vanilla.
Whisk the wet ingredients into the dry ingredients, combining thoroughly until the mixture is smooth.
Fill a 10-inch skillet with a 1-inch deep layer of cooking oil.
Heat the oil to about 375 degrees. If you don’t have a deep-fat frying thermometer, that’s okay. Just heat the oil to medium.
For the cakes to cook quickly without becoming saturated in oil, you want it to be the correct temperature. To test this, simply dribble a tablespoon full of batter into the oil.
Bubbles should immediately surround the batter, and it should sizzle.
If it pops and sputters, the oil is too hot. If it just sits there and doesn’t cook very quickly, the oil needs to be hotter. Your blob of batter should brown in about 2-3 minutes on one side.
Once you’re sure the oil is an appropriate temperature, you can start creating the funnel cakes.
Bring your batter bowl right next to the stove where you’ll be working. Using one hand, cover the funnel opening with one of your fingers to keep the batter from pouring out. Put about 1/4 cup batter into the funnel.
Holding the funnel full of batter over the hot oil, remove your finger and allow the batter to pour out of the funnel opening into the hot oil.
If the batter won’t stream out of the opening because it’s too thick, return it to the bowl and add a little bit of milk or water to thin it a bit.
Drizzle the stream of batter all around the pan, crisscrossing the dough lines so that the mat of dough threads will stick together into a large cake.
Cook the cake until you can see the edges of the dough threads beginning to turn a light brown.
Using a slotted spatula, quickly flip the cakes to cook the back-side.
Be very careful when you turn the cakes to avoid splattering yourself with hot oil. It’s best if you flip the cakes away from you to keep any splatters off of yourself.
When the cake is golden brown on both sides, remove it and place it on a paper towel-lined plate to drain the oil.
Shake powdered sugar generously over the surface of the cake and serve it piping hot.