Preheat oven to 350 degrees F. Line a 15x10x1-inch pan with foil, extending foil over the pan edges. Lightly grease foil. Set pan aside. In a large bowl, use a pastry blender to cut 1/2 cup butter into cookie mix until mixture resembles coarse crumbs. Press mixture evenly onto the bottom of the prepared pan. Bake in the preheated oven for 10 minutes or until set.
In a large bowl, combine cream cheese and sugar. Beat with an electric mixer on medium speed until combined. Add eggs, one at a time, beating on low speed after each addition until just combined. Stir in pumpkin, vanilla, pumpkin pie spice, and salt. Pour pumpkin mixture onto the hot crust.
Bake for 30 to 35 minutes more or until mixture is slightly puffed around edges and just set in center. Cool completely in pan on a wire rack.
In a small microwave-safe bowl, combine chocolate pieces and the 1/4 cup butter. Microwave on 100% power (high) for 30 to 60 seconds or until softened; stir until smooth. Drizzle chocolate over the cooled bars and carefully spread evenly. Gently press pecan halves evenly across top of bar mixture. Cover and chill for 2 to 24 hours. Using the edges of the foil, lift the uncut bars out of the pan. Cut into bars, cutting straight down with a large knife.
Place bars in a single layer in an airtight container; cover. Store in the refrigerator for up to 3 days.