Cook over medium heat until the blackberries have cooked down and the blackberry sauce has thickened up to a jam consistency.

Remove from heat and set aside to cool while you make the blondie batter.

Pre-Heat your oven to 350 degrees F.

In a mixing bowl, mix melted butter and brown sugar until well combined.

Add the egg and the egg yolk, along with the vanilla, to the sugar and butter. Mix thoroughly.

In a separate bowl, mix together flour, salt, baking powder, and cornbread mix.

Combine the dry flour mixture with the sugar and egg mixture. Mix thoroughly until the batter has just come together. It will feel a little thick (This is what you want).

In a greased 9x9 baking dish, take half of your blondie batter and spread it evenly over the bottom of the dish.

Next, take half of your blackberry sauce and spread it evenly over the bottom layer of blondie mix.

Lastly, take the remaining blondie batter and spread it evenly over the layer of blackberry sauce. Pour on the remaining blackberry sauce over the top, and swirl across the top of the batter. (The layers from the bottom up should be: batter, blackberry, batter, blackberry)

Place blondies into your pre-heated oven, and bake for 40-45 minutes, or until the edges have gotten golden brown and the center has set.

Once fully baked, remove from the oven, allow to cool slightly, and cut into 9 equal pieces. Serve and enjoy!