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Preheat oven to 350 degrees F.
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Line a baking sheet with parchment paper.
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Whisk together the flour and baking powder and set aside.
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Beat the butter and brown sugar until combined.
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Add eggs, vanilla extract, and dark rum.
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Turn the mixer speed down to low and add the dry ingredients.
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Beat in the pistachios, pineapple, and butterscotch chips.
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Divide the dough in half.
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Shape each with your hands on one side (lengthwise) of the baking sheet into a long log about 3 inches wide.
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Pat the top down to make it flat.
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Repeat with the other half, making sure there is at least 2 inches between the logs.
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Bake for about 20-25 minutes until the logs turn golden brown.
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Turn the oven temperature down to 250 degrees.
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Remove the baking sheet from the oven and let the biscotti loaves stand about 10 minutes.
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Slice each log into 1-inch pieces.
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Lay them on their sides and return to the oven for 10 minutes or until completely dry.
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Transfer to a wire rack to let cool completely.
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Plate and serve.