Puff pastry is made by a time-consuming process of folding and rolling out dough brushed with butter. These layers expand during baking, giving it a "puff" effect that's light and flaky—the perfect base for appetizers and desserts.
Thaw frozen phyllo pastry. In small microwaveable bowl, microwave butter until melted. Place 1 sheet of the phyllo on work surface; keep remaining sheets covered with damp towel (to prevent drying out). Lightly brush phyllo with some of the butter. Top with second sheet of the phyllo; lightly brush with some of the remaining butter. Repeat with remaining phyllo and butter.
Halve layers lengthwise; cut crosswise into thirds to make 6 squares. Press 1 square into bottom and up side of each well of 6-count muffin pan, pointing overhang outward. Bake in 400°F oven until golden, about 6 minutes. Let cool completely in pan. (Make-ahead: Store in airtight container for up to 3 days or freeze for up to 1 month; reheat in 350°F oven until crisp, about 3 minutes.)
Makes 1 batch (6 pieces).