In a large mixing bowl, whisk together the eggs and milk until smooth. Add vanilla extract, cinnamon, and brown sugar; stir until combined.

Carefully slice each King's Hawaiian roll in half, ensuring they're still intact. Poke holes in the bottom for absorption.

Dip each half into the custard mixture for about 30 seconds on each side, ensuring they're moist.

Heat a skillet over medium-low heat, add butter and melt. Swirl to coat the skillet.

Place the soaked rolls cut side down on the skillet. Cook for 3-4 minutes until golden brown, then flip and cook again.

Transfer to a warm plate and serve immediately with desired toppings like powdered sugar or fresh berries.