Preheat oven to 350 degrees Fahrenheit. Melt stick and tablespoon of butter in small saucepan over medium-low heat until milk solids brown and butter smells nutty. Remove from heat and let cool.
Toss pecans with pinch of maldon sea salt and 1 tbsp of browned butter. Scatter on parchment lines baking sheet and bake about 8 minutes or until toasted. Remove from heat and cool to room temperature.
Line 1/4 sheet pan (or 10x10) with parchment, butter and flour.
In a large bowl, beat together brown butter and both sugars. Add vanilla and rum until incorporated then beat in egg. In a separate bowl, blend flour, salt, baking soda and cinnamon then blend into butter mixture, stirring until no lumps remain. Fold in toasted pecans and 3/4 of the chocolate chips, reserving 1/4 cup.
Transfer batter into prepared pan. It will be very thick. Wet fingers and spread batter evenly across pan. Sprinkle reserved chocolate chips and generous pinch of maldon sea salt (really work it through your fingers so the flakes aren't too big) across pan and gently press into batter.
Bake for 18 minutes, until top is golden. Let cool completely in pan before cutting.