Baker By Nature does a great job with this stuff.
1/2 cup unsalted butter
1 cup light brown sugar, packed
1 large egg, at room temperature
1 cup flour
1/2 teaspoon baking powder
1/2 teaspoon cinnamon
3/4 cup semi-sweet chocolate chunks
1/2 cup toasted walnuts, chopped
1/2 teaspoon flaky sea salt
Preheat oven to 350 degrees (F). Line an 8×8 baking pan with parchment paper and spray parchment lightly with non-stick spray, set aside.
Melt butter in a medium-sized skillet over medium heat. Continue cooking butter, stirring frequently, until it’s a light amber color and smells slightly nutty. Remove from heat at once and cool for a few minutes before whisking in the brown sugar; beat until well combined. Add in the egg, beating until combined. Gently stir in the flour, baking powder, and cinnamon, being sure not to over mix. Fold in the chocolate chips and chopped walnuts.
Bake for 25-28 minutes, or until the edges are firm and golden and the center is just slightly wobbly. Sprinkle with sea salt. Cool in pan for at least 15 minutes before cutting.