Preheat the oven to 375°F (190°C). Grease a 24-cup mini muffin pan.

Use a rolling pin to roll the sheet of puff pastry into an 8×12-inch rectangle. (If the puff pastry is sticking, dust the surface with a small amount of all-purpose flour.) Using a sharp knife or pizza cutter, slice the puff pastry into 4 even strips length-wise. Then, cut the puff pastry cross-wise into 6 even strips so you have 24 2×2-inch squares. Press the puff pastry squares into the cups of the mini muffin pan with a pastry tamper or the handle of a wood spoon. Use the tines of a fork to dock the bottoms of the puff pastry cups 2-3 times each.

Fill each puff pastry cup with 1 teaspoon of cranberry compote, 1 cube of brie, and 1 pecan half. Bake the tartlets for 17-20 minutes, until the filling is bubbly and the puff pastry is golden-brown.

Transfer the tartlets to a platter and sprinkle them with the fresh rosemary. Add sprigs of rosemary for garnish, if desired. Enjoy the tartlets warm or at room temperature.

Mix the cranberries, orange juice, water, and brown sugar together in a skillet or saucepan. Bring the mixture to a boil, stirring occasionally, over medium-high heat.

Reduce the heat to medium-low and simmer the berries, stirring often, for 15-20 minutes or until the juices are thickened and the berries have burst. When you drag a spoon through the sauce, there should be a trail and the compote should mostly hold its shape.

Remove the compote from the heat and stir in the orange zest. Transfer the compote to a bowl and let it cool completely. It will thicken more as it cools.