Step 1: Pour 2-3 cups of vegetable oil into a deep, heavy-bottomed pot, filling it about 3 inches deep. Heat the oil to 350°F (175°C) over medium heat.
Step 2: In a medium mixing bowl, whisk together the pancake mix, egg, and milk until you have a smooth, lump-free batter.
Step 3: Take each jumbo marshmallow and dip it fully into the pancake batter, making sure it is completely coated. Gently shake off any excess batter.
Step 4: Carefully place the batter-coated marshmallows into the hot oil one at a time to avoid overcrowding. Fry them for 30 seconds to 1 minute, turning occasionally with a slotted spoon until they are golden brown on all sides.
Step 5: Using the slotted spoon, remove the fried marshmallows from the oil and place them on a plate lined with paper towels to drain excess oil.
Step 6: While still warm, optionally top the marshmallows with whipped cream, drizzle with chocolate syrup, and sprinkle with colorful sprinkles for extra fun and flavor.
Step 7: Serve immediately and enjoy your crispy-on-the-outside, gooey-on-the-inside deep fried marshmallow treats!