Heat the oven to 450ºF (230ºC). Line a baking sheet with foil and lightly coat it with cooking spray.
In a shallow dish, combine the crushed cornflakes, grated Parmesan, and Ranch dressing mix; set aside.
In a second shallow dish, whisk together the eggs and milk until blended.
Working with one tender at a time, dip a chicken tender into the egg mixture, then press into the cornflake mixture to coat. Repeat the dip in egg and coat again to double-coat each piece.
Arrange the double-coated tenders on the prepared baking sheet in a single layer. Lightly spray the tops with cooking spray.
Bake for 12–14 minutes, until the chicken is cooked through and the coating is golden and crisp.