Classic Stuffing

Arrange a rack in center of oven; preheat to 350°. Spread bread between 2 baking sheets.

Bake bread, tossing halfway through, until crispy and feels dry and the edges are just starting to turn golden, 15 to 20 minutes.

Meanwhile, in a medium skillet over medium heat, melt 3 Tbsp. butter. Cook onion and leeks, stirring occasionally, until softened, about 7 minutes. Add garlic and cook, stirring, until fragrant, about 1 minute more; season with salt and black pepper. Let cool slightly.

In a medium bowl or large glass measuring cup, whisk eggs, broth, milk, herbs, and red pepper flakes; generously season with salt and black pepper.

Increase oven temperature to 375°. Grease a 13" x 9" baking dish with a thin layer of butter.

Transfer bread to a very large bowl. Add onion mixture and egg mixture and toss to combine. Let sit at least 10 minutes or up to 1 hour.

Transfer bread mixture to prepared dish and spread in an even layer, making sure all liquid makes it into dish. Cut remaining 3 Tbsp. butter into small pieces and dot over top. Cover with foil.

Bake stuffing 20 minutes. Uncover and continue to bake until top is golden brown and crisp, 25 to 30 minutes more. Serve warm or at room temperature.