Heat oven to 400°F. In a bowl, stir together cheese, ham, half-and-half, sage and pepper. On a lightly floured surface, roll out 1 pastry sheet to a 12-inch square; cut into 9 squares. Working with one square at a time, brush edges with egg and place 1 tbsp filling in center. Fold together opposite corners of square, forming a triangle, and press together edges to seal; decorate with tines of a fork. Transfer to a baking sheet, brush with egg and prick top of each once with a fork. Repeat with remaining pastry sheet, filling and egg.
Bake 5 min. Reduce heat to 375°F and bake until puffed and golden brown, about 15 min more. Serve warm, with mustard.
For the ham, I ask the person behind the deli counter to cut it into 1/4 inch slices, so it's easy to slice and dice for this recipe. Use any extra diced ham in omelets or soup. I always double this recipe, so I have extra in the freezer for another time. They are also a great dinner accompaniment with a salad or soup!Make-ahead tip: Freeze uncooked turnovers up to 3 weeks. Bake frozen turnovers at 300°F 10 min, then increase heat to 350°F and bake 12 min more.