Separate the Hawaiian rolls into individual buns, keeping them intact (don't slice them).
In a large bowl, whisk together eggs, half and half, vanilla extract, sugar, cinnamon, and nutmeg until well combined.
Heat a large skillet or griddle over medium-low heat to ensure even cooking without burning.
Once the skillet is heated, melt 2 tablespoons of butter and coat the bottom of the pan evenly.
Dip each Hawaiian roll into the egg mixture, coating all sides, allowing any excess to drip off.
Place 4-6 coated rolls in the buttered skillet, being careful not to overcrowd the pan.
Cook for 2-3 minutes on each side (tops, bottoms, and all four sides) until golden brown, turning carefully with tongs or a spatula.
Transfer the cooked pieces to a serving plate and repeat with remaining rolls, adding more butter to the skillet as needed.
Once all pieces are cooked, dust with powdered sugar and serve with your favorite toppings like fresh fruit, maple syrup, or honey.
Notes
Heat management - Cook over medium-low heat to ensure the inside cooks through before the outside burns. If your French toast is browning too quickly, lower the heat.
Dipping technique - Don't soak the rolls too long in the egg mixture or they'll become soggy. A quick dip on all sides is sufficient.
Batch cooking - Work in small batches (4-6 rolls at a time) to avoid overcrowding the pan, which can lead to uneven cooking and steaming instead of browning.
Butter as needed - Add fresh butter between batches to prevent burning and ensure each piece gets that delicious buttery exterior.
Serve immediately - These taste best fresh off the griddle. If cooking for a crowd, keep finished pieces warm in a 200°F oven while completing the remaining batches.
Variation for smaller bites - Slice the rolls in half horizontally to make smaller French toast pieces. Reduce cooking time slightly since they'll cook faster.