How to Make It
Preheat oven to 375°F. Place phyllo on a work surface; cover with plastic wrap and a damp towel to prevent from drying out. Lightly coat a 9-inch tart pan with removable bottom with cooking spray. Microwave 1⁄4 cup of the butter in a small microwavable bowl on HIGH until butter melts, about 20 seconds. Brush 1 phyllo sheet lightly but completely with melted butter, and place, buttered side up, in prepared tart pan, pressing pastry into edges of pan. Brush another phyllo sheet with butter in the same way, and press pastry into pan, buttered side up, at a 45° angle to the first sheet. Repeat procedure with remaining 8 phyllo sheets, covering the bottom and sides of pan with a uniformly thick layer of phyllo. Trim overhanging pastry, leaving 1⁄2 inch of phyllo over the edges of the pan. Fold overhanging phyllo to inside, and press to adhere.
Microwave remaining 1⁄4 cup butter in a small microwavable bowl on HIGH until butter melts, about 20 seconds. Combine melted butter, light corn syrup, dark brown sugar, heavy cream, vanilla extract, baking soda, and salt in a bowl, stirring well. Stir in chopped toasted pecans. Pour mixture evenly into prepared pan. Bake in preheated oven until browned and bubbly, 20 to 25 minutes. Cool in pan on a wire rack 15 minutes. Remove from pan, and place on a serving plate. Serve tart warm or at room temperature with whipped cream.