Lay out pastry sheet and cut in half, forming (2) 9 ½” x 4 ¾” rectangles. Place half of the prosciutto on 1 rectangle, leaving ½” border along 1 side. Shred the Finlandia Havarti Cheese.
Sprinkle half the basil on top of the prosciutto and then top with half the Finlandia Havarti Cheese. Brush egg glaze over the plain border. Starting at long side opposite border, roll up pastry jelly-roll style. Press gently to seal the long edges. Wrap in plastic.
Repeat steps with remaining pastry, prosciutto, basil and cheese. Place pastry logs in refrigerator until firm – at least 3 hours but can be prepared up to 2 days in advance.
Position rack in center of oven and preheat oven to 400F. Line 2 large baking sheets with parchment paper. Cut logs crosswise into ½” thick rounds. Place rounds on prepared baking sheets 1” apart. Bake 1 sheet at a time until pastries are golden brown, about 20 minutes. Using a metal spatula, transfer pastries to a rack to cool. Serve warm.