Apple crumble

Here come the recipe from Pauline Chow
i try to simplify the version.
Pie Crust: (for Bottom) 180 grams all-purpose flour
1/2 teaspoon salt
110 grams unsalted butter, chilled, and cut into 1 inch (2.5 cm) pieces
Ice water (about 2 table spoon)
Apple Filling:
5-6 green apple (Granny Smith) peeled, cored, and sliced 1/4 inch thick
1/4 cup (50 grams) granulated white sugar
1/4 cup (55 grams) light brown sugar
1 tablespoon lemon juice
1 teaspoon ground cinnamon
1/4 teaspoon ground nutmeg (optional)
1/4 teaspoon salt
2 tablespoons (28 grams) unsalted butter
1 1/2 tablespoons (15 grams) cornstarch (corn flour)

Crumble (Top)
150 gm all-purpose flour
1/2 teaspoon salt
50gm chilled unsalted butter, cut into 1/2-inch cubes
1/4 cup sugar or brown sugar
1 teaspoons ground cinnamon
1/2 teaspoon salt
Preparation Method
Pie Crust:
You can use your fingertips to rub the cold butter, salt and flour together till resembles coarse meal. Follow by adding ice water to form the mixture into dough. Or use a food processor to do it. Refrigerate the dough with plastic wrap for at least half an hour to one hour.
Next, return dough onto your work surface after half an hour and place it on a lightly floured surface. Roll the pastry into a 12 inch (30 cm) circle. Gently transfer to a 9 inch (23 cm) pie pan. Brush off any excess flour and trim the edges of the pastry to fit the pie pan.
Make the Apple Filling:
In a large bowl combine the sliced apples with the sugars, lemon juice, ground cinnamon, nutmeg, corn flour and transfer the apple filling and pour into the pie crust.
For crumble topping:
Mix all ingredients in large bowl and rub in with fingertips until coarse meal forms. Stir with fork until moist clumps form, adding little water if dough is dry. Or
Blend first 5 ingredients in processor. Add chilled butter cubes; using on/off turns, cut in until mixture resembles wet sand.
Pack topping over and cover around apples. Try cover the whole pie with crumble and Do not leave any big holes especially at the rim of the pie. This is to prevent the apple juice from oozing out from the edge when the filling is cook and start bubbling.
Preheat the oven to 220 degrees.
Bake pie until topping is golden, about 40 minutes (cover top with foil if browning too quickly). Reduce oven temperature to 180 degree after 10mins. Bake until apples in center are tender when pierced and filling is bubbling thickly at edges, about 45 minutes longer.
Remove the pie from the oven and place on a wire rack to cool for about 3-4 hours before cutting. Serve warm.