Preheat oven to 350 degrees. Line a 9x13 pan with tin foil, leaving some excess on the sides so that you can remove the bars after baking.

Crush pretzels (you could do them in a plastic bag with a rolling pin or pulse them in a food processor) until they are mostly in about 1/2 inch pieces. Stir in melted butter until they are completely coated.

Evenly distribute them on the 9x13 pan and bake for 8 minutes. Remove from oven and set aside.

Increase oven temperature to 375 degrees.

In a mixing bowl or stand mixer, beat butter and sugars together until fluffy. Add the eggs and mix until well-combined. Add vanilla and mix again.

Add the flour, soda, and salt and stir until somewhat combined. Add oats and mix until completely combined. Stir in chocolate chips.

Drop the cookie dough in large clumps on top of the pretzel crust and press it evenly across the pan, making sure to press it down firmly so it adheres to the pretzel base.

Bake for 18-20 minutes, or until slightly golden in the corners. Be really careful not to overbake them - it's better to ere on the side of underbaking.

Remove and let cool, before removing from pan and slicing.