Melt blackberry jam in a saucepan over medium heat for 1-2 minutes, stirring until smooth.

Grease a 13x9 inch baking dish.

Place half of the bread cubes in the bottom of the dish.

Top with cream cheese cubes.

Drizzle the melted blackberry jam over the cream cheese and bread.

Add the remaining bread cubes on top.

In a separate bowl, whisk together eggs, half-and-half, cinnamon, and vanilla.

Pour the egg mixture evenly over the bread mixture.

Sprinkle brown sugar over the top.

Cover the dish tightly with plastic wrap or foil.

Chill in the refrigerator for 8 to 24 hours.

Preheat oven to 325 degrees Fahrenheit.

Bake the covered dish for 20 minutes.

Uncover the dish and bake for another 10-15 minutes, or until the bread is golden brown and the mixture is set.

Serve warm with desired toppings, such as maple syrup or whipped cream.