Heat oven to 350º. Line an 8-inch square pan with foil, leaving a 2 inch overhang. Lightly coat with nonstick spray and set aside. In a small bowl, whisk together flour, baking powder and salt.

In the bowl of a stand mixer fitted with the paddle attachment, beat butter and brown sugar on medium speed until light and fluffy. On low speed, beat in the egg and Chardonnay. Gradually beat in the flour mixture until just combined. Stir in the cashews and butterscotch chips.

Pour batter into prepared pan and bake for 25-30 minutes, until the edges are golden and the center has just set. Cool completely in pan set atop a wire rack. Remove from pan using foil overhang, then cut into 12 bars. Store in an airtight container for up to four days (if they last that long!).