1. Preheat oven to 300° F. Line a 9-inch square cake pan with parchment paper. (No need to grease pan.) In a stand mixer, beat the butter, sugar and salt together until butter is soft, scraping frequently. Add flavoring choice and flour. Mix just until combined, scraping down the bowl again. This is the same order as for a hand mixer. With a hand mixer, butter needs to be semi-softened first.
2. Add batter to pan in chunks. Use your hands to press evenly into pan. Smooth the top with an offset spatula. Bake for 20 minutes. Remove pan from oven. Leave the oven on.
3. While still in pan, drag the pointy end of wooden skewer over the top of cookies, slightly scoring the top. Score vertically down the center of cookies. Turn pan 45 degrees. Score 1-inch finger cookies to the left and right of centerline. This will keep cookies from cracking when cutting. Once scored, use a paring knife to cut along these lines to bottom of pan. Poke small holes in cookies about 1/3 of the way deep, with pointy end of skewer.
4. Return pan to oven for 25 to 35 more minutes, until cookies have a deep golden edge but are mostly pale across the top. Let cool in pan. Once completely cooled, dip in melted chocolate. (Melt chocolate as directed by package.) Sprinkle with pistachios, or garnish as desired. 

Per Serving: 

Calories: 210, Fat: 13 g (8 g Saturated Fat), Cholesterol: 30 mg, Sodium: 65 mg, Carbohydrates: 20 g, Fiber: 1 g, Protein: 2 g.