Defrost pastry according to package directions (about 20 minutes). Preheat oven to 425°F. Heat butter in oven-proof sauté pan (cast iron works beautifully). Over medium heat, cook pears on both sides until well-browned, 12-15 minutes. Turn pear halves cut-side up.
Sprinkle sugar onto pears and continue browning, turning once or twice, until caramelized, 2 minutes. Pour in milk, which stops caramelization, and remove from heat.
Place puff pastry on top of pears. Bake in preheated oven for 10 minutes. Reduce heat to 350°F and bake 20 minutes longer. Serve tart topped with vanilla frozen yogurt.
Amount Per Serving
* Percent Daily Values are based on a 2000 calorie diet.