INGREDIENTS
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1 2/3 cups all-purpose flour, plus additional flour for dusting pan
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1 teaspoon baking powder
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1/2 teaspoon baking soda
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1/2 teaspoon salt
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1 cup mashed ripe banana (about 2 large or 3 medium bananas)
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3 tablespoons sour cream
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1 teaspoon pure vanilla extract
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8 tablespoons (1 stick) unsalted butter, at room temperature, plus additional butter for greasing pan
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1 cup sugar
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1 large egg, at room temperature
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1 cup nuts, such as walnuts, pecans, macadamia nuts, or hazelnuts, toasted and coarsely chopped, or 3/4 cup semisweet or bittersweet chocolate chips or mini chocolate chips*