For Pecan-Praline Pieces and Powder,* line a large baking sheet with foil; set aside. In a heavy skillet place the 1/2 cup granulated sugar. Cook over medium-high heat, shaking skillet occasionally until sugar begins to melt. Do not stir. Reduce heat to low. Stir in the chopped pecans; cook about 3 minutes more or until sugar is golden brown and pecans are toasted, stirring occasionally. Pour the mixture onto the prepared baking sheet, spreading with a wooden spoon as thin as possible. Cool. Break or chop the cooled praline into 1/4-inch pieces. Set half of it aside. For Pecan-Praline Powder, place remaining broken pieces in a blender container or food processor bowl. Cover and blend or process until ground. Store in separate containers in refrigerator or freezer up to 1 week.

For crust, in a medium mixing bowl beat butter with an electric mixer on medium to high speed about 30 seconds or until softened. Add the 1/4 cup brown sugar and beat until fluffy. Add the 1 cup flour. Beat on low to medium speed just until combined.

Pat dough onto bottom and 1-1/2 inches up the side of 9-inch springform pan. Bake in a 375 degree F oven about 10 minutes or until lightly browned. Cool crust on a wire rack while preparing filling.

For filling, in a large mixing bowl beat cream cheese, the 3/4 cup brown sugar, and the 2 tablespoons flour with an electric mixer on a medium to high speed until combined. Add the pumpkin, vanilla, cinnamon, ginger, and nutmeg. Beat until combined. Add eggs all at once. Beat on low speed just until combined. Stir in the coarsely broken pecan-praline pieces, reserving the powder for the topping.

Pour filling into the crust-lined springform pan. Place the springform pan in a shallow baking pan on the oven rack. Bake in a 375 degree F. oven for 45 to 55 minutes or until center appears nearly set when shaken.

In a small bowl combine sour cream and granulated sugar. Spread over top of cheesecake.

Remove springform pan from baking pan. Cool cheesecake in springform pan on a wire rack for 15 minutes. Use a small metal spatula to loosen crust from sides of pan. Cool 30 minutes more. Remove side of the springform pan. Cool for 1 hour. Cover and chill in the refrigerator for at least 4 hours.

Just before serving, sprinkle the Pecan-Praline Powder over sour cream topping in center of cheesecake and garnish with pecan halves, if desired. Makes 12 to 16 servings.

Be extremely careful when working with the hot sugar mixture for the Pecan-Praline Pieces and Powder. Total attention must be given as things move quickly when the sugar reaches the proper temperature to caramelize. Store praline powder in an airtight container until serving time. If desired, the praline powder also can be used as an ice-cream topping.