Preheat your oven to 350.
In a large bowl, whisk together the melted butter, dark brown sugar, white sugar, vanilla, egg, and egg yolk until smooth.
Add the flour, cornstarch, cocoa powder, and baking soda, then fold together just until combined.
Fold in the chocolate chips.
Scoop 2 tablespoons of dough onto a parchment lined baking sheet, leaving space between each cookie.
Bake for 10 minutes.
As soon as the cookies come out of the oven, firmly tap the baking sheet on the counter a few times to help the cookies flatten.
Let cool completely.
In a saucepan, combine the heavy cream, whole milk, vanilla extract, and salt.
Heat over medium heat until steaming, but not boiling.
In a separate bowl, whisk together the sugar and egg yolks until pale.
Slowly pour the warm cream mixture into the egg mixture while whisking constantly.
Return everything to the saucepan and cook over low heat, stirring constantly, until the custard thickens enough to coat the back of a spoon.
Strain into a bowl and chill completely in the refrigerator.
Churn in an ice cream maker according to the manufacturer’s instructions.
During the last few minutes of churning, add the crushed pretzels and drizzle in the salted caramel.
Transfer to a freezer safe container and freeze until firm.
