For the base dough:
1 cup (2 sticks) unsalted butter, softened at room temperature for 1 hour
1/2 cup packed dark brown sugar
2 teaspoons vanilla
2 1/4 cups all-purpose flour
1 teaspoon salt
1/2 teaspoon ginger
1/8 teaspoon cinnamon
For the peach filling:
2 pounds peaches, unpeeled (about 8 peaches)
1 tablespoon sugar
1 tablespoon cornstarch
1/4 teaspoon salt
For the pecan oat topping
1/2 cup unsalted butter, softened at room temperature for 1 hour, divided
1 cup old-fashioned oats
1/2 cup all-purpose flour
1 cup pecans, finely chopped
1/4 teaspoon cinnamon
1/4 teaspoon salt
For the glaze:
3 tablespoons lemon juice, from 1 lemon
1/2 to 1 cup powdered sugar
Heat the oven to 350°F and lightly grease a 9x13-inch baking dish.
In the bowl of a stand mixer (or in a large bowl, using a hand mixer) cream the butter with the brown sugar and vanilla until light and fluffy. Turn off the mixer and add in the flour, salt, ginger, and cinnamon. Mix in the dry ingredients on low speed, just until the dough is soft and has pulled together. Press the dough firmly into the bottom of the prepared baking pan and refrigerate while preparing the filling and topping.
Roughly chop the peaches into 1/2-inch pieces and toss with the sugar, cornstarch, and salt. Set aside.
Wipe out the mixer bowl and mix 1/4 cup softened butter with the oats, flour, pecans, cinnamon, and salt until soft and crumbly. Melt the remaining 1/4 cup butter and set aside to cool.
Spread the chopped peaches over the chilled dough base. Evenly crumble the topping over the peaches, and drizzle with the melted butter. Bake for 45 minutes or until the topping is lightly browned.
Whisk together the lemon juice with enough powdered sugar to make a thin glaze. Drizzle over the bars.
Cool (or chill) for at least an hour before slicing and serving. I do recommend chilling these; they will stay fresh (and slice more cleanly) for about 5 days when stored well-covered in the fridge.