2 10x10 sheets frozen puff pastry, thawed in refrigerator
1 egg, beaten
Preheat oven to 375F.
Filling: In non-stick skillet or pot over medium heat, cook beef (or pork), onions, Dijon, thyme salt and pepper, stirring often, until cooked through. Remove from heat. Stir in breadcrumbs and eggs; mix well. Optional: Use immersion blender, or by transferring to blender or food processor, blend until desired consistency. (I prefer a fine grind but not a paste.) Let cool slightly.
To assemble: cut each sheet of puff pastry into six rectangles. By heaped spoonful, divide meat mixture evenly among lower halves of pastry pieces. Fold upper halves of pastry overtop of meat, pressing lightly. Brush with egg wash.
Bake until golden brown, about 35-40 minutes. Cool on a wire rack. Serve warm.