Melt butter in a heavy saucepan. The butter should be just barely melted - not hot and sizzling, not browned.
Add brown sugar to a large bowl.
Pour melted butter over sugar.
Stir to combine butter and sugar. Let stand 5 minutes.
Add egg and egg yolk; stir to combine.
Stir in vanilla extract.
Add flour, baking soda, cinnamon, salt, and cayenne pepper. Stir until just combined. Please see the comments about flour in the recipe notes.
Stir in chopped chocolate.
Cover, and chill dough for 30 minutes.
Toward the end of the chilling time, preheat oven to 375 F. Line baking sheets with parchment paper or silicone baking mat.
Using a medium cookie scoop (1.5 tablespoon), drop scoops of dough 2 inches apart on prepared cookie sheet.
Bake for about 7-10 minutes, or until the edges of the cookies are golden brown. The centers should look soft and slightly underdone.
Let cool on cookie sheet for 5 minutes. Remove to wire rack to finish cooling.
Correctly measuring the ingredients is key. I suggest either weighing the ingredients or aerating the flour (sifting or fluffing) and then scooping and leveling. Packing in too much flour will cause the cookies not to spread or cause the dough to be dry and crumbly.
Or scant ½ teaspoon table salt
I suggest stirring this recipe together by hand rather than using a hand or stand mixer.