Mix the ½ cup full-fat mayonnaise, 1 tablespoon dijon mustard, 1 tablespoon ketchup, 1 teaspoon kosher dill pickle brine, and ⅛ teaspoon cayenne pepper in a small bowl until combined.
Taste and season with Salt and black pepper.
Notes
Leftover smashburger sauce can be stored in an airtight container in the fridge for up to one week.
The sauce should taste creamy and well-seasoned with a hint of spice and tanginess. Want it tangier? Add more pickle brine. Want it spicier? Add more cayenne pepper. Want it sweeter? Add a bit more ketchup.