In a saucepan, whisk together 1 cup milk, egg yolks, sugar, and cornstarch until smooth. Cook over medium heat, stirring constantly, until thick and creamy. Remove from heat, stir in vanilla, and let cool slightly until spoonable. (7 minutes ⏱️)

Cut the brioche into thick 1½-inch cubes. Carefully create a small pocket in each cube and fill with the vanilla custard to create a soft, gooey center. (10 minutes ⏱️)

In a bowl, whisk together eggs, ½ cup milk, vanilla extract, and ground cinnamon until smooth and well combined. (3 minutes ⏱️)

Heat butter in a skillet over medium heat. Lightly dip each filled bread cube into the French toast mixture without soaking, then place in the skillet. Cook, turning on all sides, until deep golden brown and caramelized. (6–8 minutes ⏱️)

Transfer the Cinnamon Roll French Toast Bites to a serving plate. Dust generously with powdered sugar and drizzle with warm vanilla sauce or maple syrup. Serve immediately while creamy and melty. (2 minutes ⏱️)