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1
Position oven rack in the center of the oven; preheat the oven to 350; grease the bottom and sides of a 9 x 13 inch baking pan.
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2
Add flour, brown sugar, and salt to a food processor; pulse a few times to blend.
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3
Scatter the butter cubes over the flour mixture and process until the mixture resembles coarse meal, with a few pea-sized pieces of butter, about 6 seconds.
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4
In a small bowl, whisk together the egg, lemon zest, and vanilla extract until blended.
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5
Add the egg mixture to the food processor and process for a few seconds, just until the dough is blended but still crumbly (do not allow the dough to form a ball around the blade, or the crust will be tough.
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6
).
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7
Turn the dough out into the prepared pan; with floured fingertips, press the dough evenly into the bottom of the pan (reflour fingers as necessary); set aside.
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8
Make the filling: in a bowl, combine the sugar, cornstarch, cinnamon, and ginger; add in the blueberries and toss to coat well.
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9
Spread the blueberry mixture evenly over the crust.
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10
Make the topping: in a bowl stir together the flour, sugars, cinnamon, and salt until blended.
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11
Stir in the melted butter until the mixture comes together; sprinkle the topping evenly over the blueberry filling.
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12
Bake the bars for 48 to 50 minutes, until the topping is lightly browned and the filling is bubbling.
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13
Cool the bars completely in the pan on a wire rack.
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14
Cut into 24 bars.
