Step 1 Cut the butter and cream cheese into small cubes. In the bowl of an electric mixer fitted with the paddle attachment, combine the flour and salt on low. Add the butter and cream cheese a few cubes at a time until all are added. Mix until well combined, about 3 minutes.
Step 2 On a well-floured surface (the dough can get sticky), roll the dough out evenly into a rectangular shape. Then fold the dough into thirds as if you were folding a letter. Wrap the dough in plastic wrap and refrigerate for 30 minutes to allow it to rest.
Step 3Roll the dough out evenly about one-fourth inch thick. Cut the dough so that it will fit over the desired casserole dishes, allowing a half-inch margin all the way around. Keep refrigerated until ready to assemble.