Make your caramel in the morning. Remove the labeling from the sweetened condensed milk and place the can on its side in a pot of boiling water. Make sure the water covers the top of the can at all times (you will have to pour in more water from time to time). Lower the heat and simmer for 2 1/2 hours. Allow the can to cool until it’s just warm, then open and stir in salt. Set aside.
Heavily grease a tart pan with a removable bottom. In a standing mixer with a paddle attachment, beat the butter and ground pretzels for 2 minutes on medium high speed. Beat in the egg and vanilla for an additional minute. Lower the speed and add in the powdered sugar, cocoa, and flour, mixing until combined. Remove dough from mixer and form into flattened disk.
Place dough between two large pieces of plastic wrap and roll out into a large circle. Your circle should be 1 1/2 inches larger than the size of your tart pan. Remove top layer of plastic wrap and flip the dough into the tart pan. Press dough into the pan and patch up any spots with extra dough. Use a sharp knife to trim excess dough, forming a clean edge. Loosely cover with plastic wrap and refrigerate for at least 30 minutes.
Preheat oven to 350°F. Create air pockets in the dough by stabbing the bottom a few times with a fork. Line the dough with parchment paper and fill with dry beans, rice, or pie weights. Bake for 15 minutes, then remove weights and parchment paper and bake for an additional 10 minutes. Place in refrigerator to cool.
After 15 minutes of cooling the crust, pour in the salted caramel. Place in fridge for 30 minutes.
Make your chocolate top. Heat the cream in a small saucepan until it’s simmering and starting to steam (not boiling). Remove from heat and stir in chocolate chips. Once fully combined, pour over salted caramel, then top with pecans. Allow to cool completely in fridge for at least 2 hours, then top with sea salt flakes and serve!