Step 1Cut the butter and cream cheese into small cubes. In the bowl of an electric mixer fitted with the paddle attachment, combine the flour and salt on low. Add the butter and cream cheese a few cubes at a time until all are added. Mix until well combined, about 3 minutes.
Step 2On a well-floured surface (the dough can get sticky), roll the dough out evenly into a rectangular shape. Then fold the dough into thirds as if you were folding a letter. Wrap the dough in plastic wrap and refrigerate for 30 minutes to allow it to rest.
Step 3Roll the dough out evenly about one-fourth inch thick. Cut the dough so that it will fit over the desired casserole dishes, allowing a half-inch margin all the way around. Keep refrigerated until ready to assemble.
Step 1Heat the oven to 350 degrees. Toss the carrots, parsnips, turnips, garlic, potatoes and onions with the thyme, oil and salt and pepper to taste.
Step 2Spread the vegetables out on a sheet pan and roast in the oven until almost cooked through, about 40 minutes. Discard the thyme sprig and set the vegetables aside.
Step 3Rinse and dry the chard. In a large saute pan, melt the butter over medium-high heat, then add the shallots and chard. Lightly saute just until the color turns bright, about 30 seconds to a minute. Season to taste with salt and pepper and set aside.
Step 1Heat the oven to 375 degrees. In a 2-quart saucepan over medium-low heat, melt the butter and saute the onions with the thyme until the onions are translucent, about 8 to 10 minutes.
Step 2Add the flour and mix well with a whisk, stirring until the mixture incorporates and forms a pale roux, 2 to 3 minutes. Add the white wine and stir to blend.
Step 3Meanwhile, in a separate pot, carefully bring the milk to a boil. Carefully add the hot milk to the sauce and bring it to a boil to allow to thicken. Remove from the heat and season with salt, pepper and grated nutmeg.
Step 4In a large mixing bowl, combine the root vegetables, the chard and enough bechamel to coat the vegetables. Check the seasoning and adjust if necessary.
Step 5Fill the casserole dishes with the bechamel-coated vegetables. Place the cut dough over the casserole dishes and push the center of the dough down to touch the vegetables. Using your fingers or a fork, crimp the edges of the dough all the way around the casserole dish. Using a paring knife, cut a half-inch slit in the center of the dough.
Step 6In a small bowl, whisk the egg and use a pastry brush to brush egg wash over the dough thoroughly. Bake the pot pies for about 45 minutes, or until dough is golden brown.
Step 7Toss the spicy cress and shallots in a mixing bowl. Add the lemon juice and olive oil to cover the greens. Toss and season with sea salt. Serve the pot pie hot out of the oven with a bunch of spicy cress salad on top.