Brown 1 stick (114 grams) of the butter using your favorite method for browning butter. I like to melt it in a small saucepan over medium low heat, swirling often as it melts and watching for browned bits to form. Remove from heat.
Allow the browned butter to cool while you weigh out the flour.
Mix the 270 grams flour with the baking soda and salt. Set the flour mixture aside.
In the bowl of a stand mixer, beat the remaining ½ cup (1 stick) butter with the brown sugar for 3 full minutes, scraping the side of the bowl often.
Beat in the vanilla and molasses.
Add the cooled browned butter and the granulated sugar to the mixing bowl and beat for 2 more minutes.
Add the egg and egg yolk, and stir until blended, then beat for about 30 seconds.
Add the flour mixture and stir until blended, then stir in the chocolate chips and pecans (if using).
Using a medium cookie scoop or a generously rounded tablespoon measure, scoop dough into balls and arrange on a plate or cookie sheet lined with plastic wrap. Chill the dough balls for an hour or overnight or until ready to bake.
Preheat the oven to 350°F. Have ready two ungreased baking sheets or if you prefer, line with parchment. I like to bake these directly on the clean baking sheets.
Set the dough balls 2 ½ inches apart on sheets. If desired, sprinkle with a little salt. This balances out the sweetness.
Bake the cookies for 12 to 15 minutes, until they're golden brown.
Remove them from the oven, and allow them to rest on the baking sheet for at least 5 minutes before moving them.