For the dough: Combine the flour, granulated sugar and salt in a large bowl. Add the oil and 1/2 cup water and stir to combine. Turn onto a floured work surface and knead, dusting with flour as needed, until smooth and slightly sticky, 5 to 7 minutes. Cover with plastic wrap or a kitchen towel and let rest at room temperature while you prepare the filling.
For the filling: Melt the butter in a small saucepan, then stir in the cream. Place the sweet potatoes in a large bowl and fold in the butter and cream, followed by the brown sugar, spices and a pinch of salt. Stir until smooth.
For the topping: Preheat the oven to 400 degrees F. line 2 baking sheets with parchment paper.
Mix together the pecans, butter, brown sugar, cinnamon and salt in a small bowl. Divide the dough into 12 balls on a work surface dusted with flour, then roll them out into 4-inch circles and brush them with a thin layer of egg. Top with a big scoop of the sweet potato filling and sprinkle with the pecan topping. Fold the edges up and over the filling to form a triangle, overlapping the corners and pinching them to seal. Transfer to the baking sheets an inch or so apart, then brush the outsides with egg wash and bake until lightly golden, 20 to 25 minutes. Let cool slightly before serving or serve at room temperature.