Heat the oven to 425°F. Put the cranberries and brandy or Cognac in a small bowl and let soak while you prepare the other ingredients. Melt the butter in a wide, heavy-based skillet over medium-high heat. Add the brown sugar and cook, stirring, until the mixture is bubbly, about 2 minutes. Add the pears and salt. Continue cooking over medium-high heat until most of the pears’ liquid has been released and cooked off, 4 to 5 minutes. Add the cranberries and brandy and keep cooking and stirring until the pears are just surrounded by a syrupy glaze, about another 3 minutes. Add the lemon juice and stir to blend. Spread the filling in a thin layer on a plate or baking dish and chill in the freezer while you roll the dough.
On a lightly floured surface, roll the dough to a 12-inch square and cut it into four even squares. Put one-quarter of the filling into the center of a square, dab the edges of the dough lightly with water, fold over to make a triangle, and press the edges together very firmly to seal. Transfer to a parchment-lined or nonstick baking sheet. Repeat with the other three turnovers. Cut three 1-inch slashes in each turnover for steam to vent. Brush the tops of the turnovers with the cream, if using. Bake until they’re deep golden brown on the top and bottom and the pastry no longer seems doughy in the center, 18 to 22 minutes. Let them cool for a few minutes and then serve warm.