In small skillet, melt the butter over medium-low heat. Add the garlic, and cook, stirring occasionally until softened and fragrant, about 8 minutes. Cool slightly.
On a lightly floured surface, roll out half of the pastry into 12 x 10 inch rectangle. Brush with half of the garlic butter, leaving a one-half-inch border on all sides. Sprinkle with half of the sage, then half of the cheese. Lightly brush the border with the egg.
Starting at the short end, roll to the center of the rectangle. Roll up the other side to meet in the center. Gently turn over and lightly brush all over with egg. Using a serrated knife, trim the ends and cut into one-half-inch thick slices. Place on greased or parchment lined baking sheets and press down lightly. Repeat with remaining pastry. Cover and refrigerate for 1 hour or up to 8 hours.
Preheat the oven to 425ºF. Bake until puffed and golden, 15 to 20 minutes.