For the Peach Cobbler Filling:

1. Prepare the Peaches:
   Drain two of the peach cans and add only the peaches to a large pot. Add the third can with its syrup, along with the butter.
2. Melt and Combine:
   Set the pot over medium heat and cook until the butter is fully melted, stirring occasionally.
3. Add Flavorings:
   Stir in the granulated sugar, cinnamon, nutmeg, and vanilla. Bring the mixture to a gentle boil.
4. Make the Slurry:
   In a small bowl, whisk 3 tablespoons of hot peach syrup (taken from the pot) with the flour until smooth. Pour the slurry back into the pot and stir well.
5. Thicken the Filling:
   Continue cooking for 30–40 minutes, or until the syrup thickens and coats the back of a spoon. Taste and adjust the sugar or spices if needed.
   Remove from heat and let it cool and thicken further while preparing the crust.

For the Pie Crust:

1. Mix Dry Ingredients:
   In a medium bowl, whisk together the flour, sugar, and salt.
2. Cut in the Butter:
   Add cold butter cubes and use a pastry cutter (or your fingers) to blend the butter into the flour until it forms coarse crumbs.
3. Add Water:
   Gradually add cold water, starting with ½ cup. Mix until a dough forms, adding more water if needed. Knead briefly until the dough comes together—it’s okay if some flour remains in the bowl.
4. Chill the Dough:
   Divide the dough into two equal balls. Wrap each in plastic wrap and refrigerate for 35–45 minutes.

To Assemble the Cobbler:

1. Preheat Oven:
   Preheat your oven to 375°F (190°C).
2. Roll Out the Bottom Crust:
   Lightly flour a clean surface. Roll out one dough ball to about ⅓-inch thickness. Place it into a 9×13-inch baking dish, covering the bottom and slightly up the sides.
3. Add the Filling:
   Using a slotted spoon, transfer the peaches (without too much syrup) into the crust. Then pour in the remaining syrup—use at least ⅔ of it, depending on how juicy you prefer your cobbler.
4. Top with Crust:
   Roll out the second dough ball and place over the filling. Decorate as desired—lattice, full cover with slits, or cut-outs.
5. Finish & Bake:
   Brush the top crust with the egg wash and lightly sprinkle with ground cinnamon.
   Bake for 40–45 minutes, or until the crust is golden brown and crisp.
6. Cool & Serve:
   Allow the cobbler to cool slightly before serving. Enjoy warm on its own or with a scoop of vanilla ice cream.