Pre-heat oven to 350 degrees. Grease 9x13 glass pan with butter and set aside.
In a large glass bowl, melt butter. Stir in brown sugar until well combined.
Stir in xanthan gum and baking soda. Add flour blend and oats and stir until everything is mixed well together.
Press about 2/3 of the batter into the pan. It will be a thin layer, but make sure you have enough in an even layer to all the edges of the pan.
Bake for 10-12 minutes. The dough will NOT be set. CAREFULLY pour the WARM caramel sauce over the cookie base layer. Smooth it carefully around the dish to create an even layer. It's okay if some of the dough comes up and mixes with the caramel sauce, but try your best not to pull up too much of the cookie base as you are spreading the caramel sauce.
Sprinkle chocolate chips evenly around the dish. Top with remaining dough sprinkled around.
Return to oven and bake about 19-21 minutes or until edges are nicely browned. The middle will still look slightly uncooked, but not jiggly, it still needs to be set. It will continue to harden as the dessert cools, and as the caramel layer cools too.
Let cool a MINIMUM of one hour. I prefer to cool this several hours before cutting into it. The caramel needs time to solidify again.
Cut into about 24 bars. Serve alone or with vanilla ice cream