In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and both sugars together on high until light and fluffy.
Add in the milk and vanilla and beat until combined.
Turn the mixer to medium and add the flour and salt. If your dough is too dry, add in another tablespoon of milk.
Turn the mixer off and fold in the mini chocolate chips.
Roll the dough into small balls (about 1tbsp each), and place each dough ball between two pretzels like a sandwich.
Place the dough stuffed pretzels on a baking sheet lined with parchment paper and freeze about 10-20 minutes.
While the dough is chilling, melt the chopped chocolate or chocolate chips with the coconut oil. You can microwave the chocolate in 30 second increments, stirring well between each.
Dunk half of each dough bite into the melted chocolate and sprinkle with flaky sea salt if desired.
Let the chocolate harden. You can speed this up by popping them into the fridge.