Preheat the oven to 350°.
In a small saucepan over medium heat, add the butter, stirring often as it cooks, until it foams. Watch carefully for the butter to brown after it foams, 5–8 minutes total. Pour into a bowl, making sure to scrape everything out of the pan, including the browned bits, and let the butter cool down for 10 minutes in the fridge before continuing with it.
Whisk the flour, baking soda, and salt together.
In a separate bowl, cream the cooled browned butter and sugars, then beat in the vanilla and eggs.
Add the previously whisked dry ingredients and mix until blended.
Mix in the toffee, pretzels, and chocolate chips. Let the dough sit on the counter in the bowl for 15 to 30 minutes.
Using an ice cream scoop, scoop out 1.25" round balls of dough and place on an un-greased cookie sheet. Using this size of dough ball, I fit about 12 cookies on my standard-sized cookie sheet.
Bake 11 to 14 minutes, or until edges of cookies begin to brown, then let them cool on the cookie sheets.