Preheat the oven to 350°F (175°C).

In a medium bowl, whisk together whole milk, room temperature eggs, and the seeds from the vanilla bean until smooth and frothy, about 2-3 minutes.

Strain the custard mixture through a fine sieve into another bowl to remove lumps for a velvety texture.

Place thick-cut bread slices in a shallow baking dish and pour the custard mixture over, ensuring each slice is covered.

Allow the bread to soak in the custard for at least 10 minutes, turning gently halfway through.

Transfer the dish to the preheated oven and bake for 25-30 minutes until the edges are golden brown and the center is slightly jiggly.

For an extra crispy topping, switch to broil mode during the last 1-2 minutes, keeping a close eye to prevent burning.

Remove from the oven and let cool for 5 minutes before dusting with powdered sugar and serving warm.