Grease your slow cooker insert with butter or a non-stick cooking spray.

Cut the bread into bite-sized cubes or thick slices and place them in an even layer in the greased crockpot.

In a large mixing bowl, combine milk, eggs, vanilla extract, cinnamon, and brown sugar; whisk until well blended.

Pour the custard mixture evenly over the bread cubes and gently press down, then cover and refrigerate for at least 6 hours or overnight.

Dot the top with butter and sprinkle brown sugar before cooking.

Cook on high for about 2.5 hours or on low for 4.5 hours until the center is set and the edges are golden brown.

Serve warm, garnished with fresh berries, maple syrup, or nuts.