For the Brown Sugar Crumble:

1. Preheat oven to 350°F. Line a baking sheet with parchment paper.
2. In a medium bowl, whisk together flour, brown sugar, cinnamon, nutmeg, and salt until thoroughly combined.
3. Melt butter in a saucepan over medium-low heat until it stops popping and the milk solids begin to brown slightly.
4. Pour browned butter into the dry ingredients, making sure to scrape in all browned bits from the pan.
5. Mix with a spatula, then use your fingers to break the mixture into various sized pieces.
6. Spread on the prepared baking sheet and bake for 10 minutes.
7. Remove from oven and allow to cool completely. (The crumble will still be soft but will harden as it cools.)

For the Pie Dough:

1. Combine flour, sugar, and salt in a bowl.
2. Add cold butter cubes and work them into the dry ingredients using fingers or a pastry cutter until mixture resembles small peas.
3. Mix ice-cold water with a splash of lemon juice, then gradually add to the flour mixture, stirring with a spatula until dough just holds together when squeezed.
4. Turn dough onto a lightly floured surface and gently press together, folding it over itself until it begins to hold together. Do not overwork!
5. Shape into a 1-inch thick disk, wrap in plastic, and chill for at least 45 minutes.
6. Roll chilled dough on a well-floured surface to a 12-inch circle, about ⅛-inch thick.
7. Fold dough into quarters, place in 9-inch pie plate, unfold, and gently press against bottom and sides.
8. Fold overhanging dough under itself and crimp edges as desired.
9. Refrigerate prepared crust for 30-60 minutes.

For the Peach Filling:

1. Preheat oven to 400°F. Place a half baking sheet in the oven while preheating.
2. Peel about two-thirds of the peaches, leaving the rest unpeeled for color and flavor.
3. Cut all peaches into 1-inch chunks and place in a large bowl.
4. Sprinkle with lemon juice and gently toss to coat.
5. In a separate bowl, whisk together sugar, flour, cinnamon, nutmeg, and salt.
6. Pour this mixture over the peaches and fold gently to combine.
7. Let sit for 5 minutes, taste, and add more sugar if desired (2 tablespoons at a time).
8. Stir in vanilla extract just before adding to pie crust.

Assembling and Baking:

1. Spoon peach filling into chilled pie crust, spreading evenly.
2. Top generously with all of the crumble, leaving a small edge (about ⅛-inch) around the crust visible.
3. Place pie on the preheated baking sheet and bake at 400°F for 20 minutes.
4. Without opening the oven, reduce temperature to 350°F and continue baking for 40-45 minutes, until center has risen and peach juices are bubbling at the edges.
5. If crust begins to darken too quickly, cover edges with a pie shield or aluminum foil.
6. Remove from oven and cool on a wire rack for at least 2-3 hours before slicing.