Line a jelly roll baking pan with wax paper, parchment paper, or greased aluminum foil. Dampening the pan before lining with wax paper prevents it from slipping around.
Microwave the chocolate chips at half power for a minute. Stir. If chocolate is not smooth and completely melted continuing microwaving at half power, in 20 second intervals, stirring after each interval. Spread over wax paper. I wish I would have left my chocolate layer a little thicker.
Microwave peanut butter and butter at half power for 30 seconds. Stir. The peanut butter should be pourable. If it’s still thick, continue microwaving at 15 second intervals until it is pourable. Drizzle melted peanut butter over the chocolate layer.
Microwave caramel bits and milk at half power for one minute. Stir. If caramel is not completely melted and smooth, continue to microwave for 20 second intervals until smooth. Drizzle over chocolate and peanut butter layer.
Using a knife, gently swirl all the layers together. Be careful not to over swirl. Sprinkle crushed pretzel over bark. Press into the bark with the back of a pancake turner. Sprinkle bark with sea salt.
Set in refrigerator to cool. Break into pieces.