Freeze the Marshmallows Place the 20 large marshmallows in the freezer until fully frozen. This step is essential to keep them from melting too quickly while frying.

Heat the Oil Pour canola oil into a 5-quart Dutch oven to a depth of 3–4 inches, or fill an electric deep fryer to the fill line. Heat the oil to 375°F (190°C).

Prepare the Batter In a medium mixing bowl, whisk together the whole milk, room-temperature egg, and vanilla extract until fully combined.

Add Pancake Mix Gradually whisk in the buttermilk pancake mix until a smooth, thick batter forms with no lumps.

Coat the Marshmallows Remove the frozen marshmallows from the freezer. One at a time, dip each marshmallow into the batter, fully coating all sides.

Fry the Marshmallows Carefully lower the battered marshmallows into the hot oil using a slotted spoon or tongs. Fry in small batches for 30–45 seconds, turning gently, until golden brown and puffed.

Drain Excess Oil Remove the fried marshmallows from the oil and place them on a plate lined with paper towels to drain.

Add Toppings and Serve While still warm, dust with powdered sugar or top with whipped cream, chocolate sauce, or rainbow sprinkles as desired. Serve immediately.