Preheat the oven to 350 degrees F (175 degrees C).

Make sauce: Melt together caramels and heavy cream in a medium saucepan over low heat; stir occasionally until smooth. Set sauce aside.

Make bars: Mix together flour, oats, brown sugar, baking soda, and salt in a medium bowl. Stir in melted butter until well blended. Press 1/2 of the oat mixture into the bottom of a 9x13-inch baking dish.

Bake crust in the preheated oven for 8 minutes. Remove from the oven. Sprinkle crust with chocolate chips and walnuts. Drizzle with sauce and crumble remaining oat mixture on top.

Continue baking until the top is lightly toasted, about 12 more minutes. Cut into squares while still warm.