Preheat oven to 350F and line an 8X8 baking dish with foil and grease heavily.
In a medium bowl mix, together crushed pretzels and 6 tbsp melted butter. Press into bottom of prepared pan.
In the same bowl mix together ½ cup melted butter and sugars. Add in vanilla extract and egg until combined.
Add flour, baking soda, salt and mix until just combined.
Fold in chocolate chunks and M&M's, I reserved a few to sprinkle on top of batter.
Bake for 24-26 minutes, until light and golden brown.
