Slice the tops off the peppers and remove the seeds; cut each pepper into 1/4-inch rings. Place 1 inch oil in a soup pot and heat over medium-high heat until hot but not smoking.

Meanwhile, in a medium bowl, with an electric beater on medium speed, beat milk, flour, cornstarch, baking powder, and salt until smooth. Dip a few pepper rings into the batter, allowing excess batter to drip back into bowl. Reduce heat to medium and carefully place rings in oil one at a time; fry 2 to 3 minutes, until golden, turning halfway through cooking. Drain on paper towels.

Continue until remaining pepper rings are fried, adding more oil as needed. Serve immediately, or keep warm in a 200°F. oven until ready to serve.