Preheat oven to 425°F. and lightly butter a baking sheet.
On a lightly floured surface cut out 24 pastry rounds from pastry sheet with a 1 1/2-inch round cutter and arrange 1 inch apart on baking sheet. Brush tops of rounds with some egg wash (be careful not to drip down sides of rounds) and bake in middle of oven until puffed and golden brown, about 12 minutes (rounds will puff unevenly). Transfer rounds with a spatula to a rack and cool slightly. Trim bottoms of rounds if necessary to create level pastries and cool completely on rack. Pastry rounds may be made 2 days ahead and kept in a sealable plastic bag at room temperature.
Break Stilton into 24 small pieces (about 1/4 inch) and bring to room temperature. Top each pastry round with 1 piece Stilton and 1/2 teaspoon jam and serve at room temperature.