Preheat the oven to 375.
Add the cream cheese, cheddar, beer, buffalo sauce and cornstarch to a blender or food processor. Process until smooth.
Add the chicken, pulse once or twice to combine (do not over process or the chicken will be destroyed).
Roll the puff pastry sheets out on a lightly floured surface. Using a 3-inch biscuit cutter, cut out 24 circles. Press the circles into the wells of a mini muffin tin, poke the circles one or twice with a fork to create air holes in the bottom.
Fill the puff pastry 2/3 full with the cream cheese mixture.
Bake at 375 for 18-20 minutes or until puff pastry is light golden brown.
Add to a serving platter, sprinkle with chopped chives.