Preheat oven to 375 degrees F. Have ready a couple of ungreased cookie sheets.
In a bowl, thoroughly stir together the flour, baking powder, baking soda and salt
In a mixing bowl, using an electric mixer, beat together the clarified butter (or shortening) and regular butter until creamy. Add both sugars and continue beat just until blended. Add egg and vanilla and beat just until blended. By hand, stir in the flour mixture. When blended, stir in the chocolate chips and nuts (if using).
Scoop up measuring tablespoons of dough and arrange on the baking sheets spacing about 2 ½ inches apart. Alternatively, put the scoops on a plate, cover and chill until ready to bake. Chilling improves the dough. It makes the cookies browner and helps them spread more evenly.
Bake on ungreased cookie sheets for 10-14 minutes or until lightly brown around the edges. Let cool on baking sheets for five minutes, then transfer to a wire rack.
Notes
About the clarified butter, I'm not an expert and recommend you read a tutorial if you've never done it. For this recipe, you’ll need to start with a stick (½ cup 4 ounces) of unsalted butter to make ⅓ cup (2.3 ounces) clarified. Melt the butter over medium heat until it starts to separate. Skim any whey that's risen to the top, then pour into a bowl and let cool. As it cools, the milk solids sink. Pour off the clear butter. Save the milk solids for something else or discard.