Roll out the puff pastry to a 10.5 or 11-inch square—they usually come in 9-inch squares, so this will require just a brief amount of rolling. Take a plate that has a similar circumference to the skillet you want to bake the pot pie in and lay it over the puff pastry. Cut the dough into a circle that is slightly larger than the plate (the dough will shrink as it bakes), then cover the dough and set it in the refrigerator until ready to use. Heat the oven to 400°F. Then heat a 10-inch oven-safe skillet (or similar) over medium heat and add 1 tablespoon of olive oil. When the pan is hot, add the leeks and cook, stirring often, until soft and lightly caramelized, 5 to 7 minutes. Add the kale and cook, stirring occasionally, until soft and wilted, another 3 to 5 minutes. Season with a pinch of salt before removing to a medium mixing bowl. Return the pan to the heat and add the remaining 2 tablespoons of olive oil. When the pan is hot, add the mushrooms and cook, stirring occasionally, until soft and lightly browned, 8 to 10 minutes. Season with a generous pinch of salt in the last few minutes of cooking. Transfer the mushrooms to the same bowl as the kale and leeks. Return the pan to the heat and add the butter (or oil). When the butter is melted, add the garlic and cook, stirring very frequently for a minute or so, until the garlic is fragrant but not browned. Add the flour and whisk until the mixture forms a paste. Continue whisking very frequently for 3 to 4 minutes to cook the flour until the mixture turns a light tan color. Add the wine and whisk constantly until the mixture forms a thick paste. Then add the broth a little at a time, whisking all the while to prevent lumps. Continue whisking constantly until the mixture comes to a boil, then reduce the heat, add the rosemary, and let simmer, stirring frequently for 3 to 5 minutes. Turn off the heat and stir in the heavy cream. Add the kale, leeks, and mushrooms back into the pan, along with the rinsed and drained beans. Stir until all the ingredients are evenly dispersed in the pan. Place the circle of puff pastry over the stew, working quickly, as the pastry will immediately become a bit melty. The pastry will be larger than the pan, so simply allow the excess pastry to climb up the sides of the skillet. Brush the top of the pastry with heavy cream (milk, milk alternatives, half-and-half, melted butter, and egg wash are all fine alternatives), and cut a few vent holes in it. Bake for 30 to 35 minutes or until the crust is golden brown and the filling is bubbling.