1. Preheat oven to 400 degrees F. Cut four 24x15-inch sheets of parchment paper. Fold each sheet in half, forming 15x12-inch rectangles. Cut a heart shape from one of the rectangles. Use this as a guide to cut 3 more hearts from the remaining rectangles. Set hearts aside.
2. In a large bowl whisk together the flour, cream, broth, and pepper until smooth. Add the chicken and toss to coat. Add the mushrooms, carrots, leek, and peas; toss to coat.
3. Working with one at a time, unfold the parchment and mound 1/4 of the chicken mixture on one side of the heart, leaving a 3-inch border. Place 2 biscuits on each mound (refrigerate the remaining biscuits and bake another time).
4. Starting at the top of the heart, make a 1/2-inch folded edge, creasing crisply. Working your way around again, make overlapping 1/2-inch folds. Twist the tip of the heart and tuck it under the packet. Place packets on a large baking sheet (they may overlap). Bake for 20 to 25 minutes or until biscuits are golden and chicken is no longer pink.