Heat oven to 350 degrees F. Grease 15 x 10 x 1-inch jelly-roll pan with nonstick cooking spray. Drain canned sweet potatoes, reserving 3 tablespoons syrup. Mash potatoes in bowl, combining with reserved syrup.
Whisk together flour, baking powder, allspice, cinnamon, cloves and salt in medium-size bowl. In large bowl, beat butter and sugars together on medium speed until smooth and slightly lightened in color, about 2 minutes. Beat in eggs, one at a time, until incorporated. On low speed, beat in half the flour mixture. Beat in mashed sweet potato, then remaining flour mixture. Fold in the mini chips and 3/4 cup of chopped nuts.
Scrape batter into prepared pan, spreading to edges; smooth top. Sprinkle with remaining 1/2 cup chopped pecans.
Bake in 350 degree F oven for 35 to 40 minutes or until lightly browned and pecans are toasted. Cool in pan on wire rack. Cut into bars. Makes 4 dozen squares.