Peel the pears, split them lengthwise, and remove the cores. Arrange the flat side down in one layer in a large gratin dish. Sprinkle the sugar on top.
Bake for about 35 minutes. By this time, the sugar should have dissolved in the pear juices and cooked into a caramel; the pears should be tender when pierced with the point of a knife. If the pears are still hard, cook for another 5 or 10 minutes. If the sugar is caramelized but the pears are not cooked, add ½ cup water to prevent the caramel from burning during this extra cooking period. On the other hand, if the pears are cooked through before the syrup is caramelized, remove the fruit to a plate and reduce the juice on top of the stove until it caramelizes.
Add the cream to the dish and bake for 10 to 15 minutes longer, basting the pears every 5 minutes. The sauce should have reduced and thickened and be a nice ivory color. (Cooking the caramel with the cream will form a rich and delicious sauce.) Let cool. The sauce will thicken.
Serve the pears cool at room temperature, with the sauce on top, sprinkled with the pistachios.
Recipe by Make Mine Lemon at https://www.makeminelemon.com/braised-pears/