Pour the olive oil into a large, deep skillet. Heat over medium until shimmering. Add the shallots and a pinch of salt, sauce over low until just translucent.
Add the garlic, celery, and carrots. Sauté until slightly softened - about 5 minutes. Add the mushrooms and saute until nearly cooked through. We want the mushrooms to leech off as much liquid as possible before adding them to the final pie.
Once the mushrooms are in a good place add the snap peas and asparagus. Sauté them briefly. Once all the veg is sautéed to their various states of doneness, transfer them to a large bowl and set aside.
Melt the butter in the skillet. Whisk in the flour to form a roux. Add the cognac and whisk it into the roux. Slowly whisk in the milk and stir in the Dijon mustard and creme fraîche. Taste and season with salt accordingly.
Add the pinto beans to the skillet along with the sautèed vegetables and the herbs. Toss to coat. Pour the pot pie filling into a large casserole dish, cover, and let cool on the counter before thoroughly chilling in the fridge.
When you’re ready to bake the pie, preheat the oven to 375°F. In a small bowl beat one large egg. Using a pastry brush, brush the egg all over the edges of your casserole dish.
On a floured surface, roll the puff pastry out until it is wide and long enough to handily cover the top of the casserole dish. Drape the pastry over the casserole dish and tuck in the sides. Form a seal using a fork and trim off the excess pastry, leaving a good amount of overhang.
Cut a vent in the center of the pastry and brush with the remaining egg mixture. Transfer the pie to the oven. Bake for 55 minutes or until the pastry is golden. Scoop the pot pie into bowls and serve immediately.