Chocolate-Pumpkin Cheesecake Bars

Here's a Martha Stewart recipe that my sister, Cathy, passed along to me. (Yes, my fabulous, gorgeous, talented, youthful, vibrant, funny, caring and all-around wonderful sister, Cathy.)  Of course I HAD to make them because, seriously, I've never met a cheesecake bar I didn't like.  They're rich and delicious and they're the perfect thing if you're looking for something a little different from your usual pumpkin pie. They're also great because you can make them in advance and either keep them covered and chilled in the fridge, or wrapped and frozen. Better make extra because they'll be gone in no time flat!!
Thanx, Sister!

For the crust:
20 chocolate wafer cookies (half a 9-ounce package)*
2 tablespoons sugar
4 tablespoons unsalted butter, melted

For the filling:
2 packages bar cream cheese (8 ounces each)
1 cup sugar
1 cup canned solid-pack pumpkin puree
3 large eggs
3 tablespoons all-purpose flour
1 teaspoon pumpkin-pie spice
1/2 teaspoon salt
4 ounces semisweet chocolate, chopped

 Preheat oven to 350F. Line bottom and sides of an 8-inch square baking pan with parchment paper or aluminum foil, leaving an overhang on all sides. Set aside.
In a food processor, blend cookies with sugar until finely ground (you should have about 1 cup crumbs); add butter, and pulse until moistened.
Transfer crumb mixture to prepared pan, and press gently into bottom. Bake until fragrant and slightly firm, 12 to 15 minutes. Set aside to cool.
Place cream cheese in food processor; blend until smooth. Add sugar, pumpkin puree, eggs, flour, pumpkin-pie spice, and salt; process until combined. Set aside.
Place chocolate in a microwave-safe bowl; microwave in 30-second increments, stirring between each, until melted. Add 1 cup pumpkin mixture; stir to combine. Set aside.
Pour remaining pumpkin mixture into prepared pan. Drop dollops of chocolate mixture onto pumpkin mixture; swirl. Bake until cheesecake is set but jiggles slightly when gently shaken, 40 to 50 minutes.
Cool in pan. Cover; chill until firm, at least 2 hours (and up to 2 days). Using overhang, transfer cake to work surface. With a knife dipped in water, cut into 16 squares. Serve.

Tips:
* Instead of buying chocolate wafers and then adding butter and sugar, I found it easiest to just throw about 15-18 regular Oreos into the food processor and process until they're fine crumbs. No need to add melted butter or sugar because the creme filling is already in there!
When you cut them, be sure to dip your large knife into very hot water, just as the recipe directs. It's a great tip for getting perfectly clean cuts. You could always just clean your knife under very hot running water between each cut.
For an easy variation, try butterscotch chips or white chocolate instead of the semisweet chocolate.
To make a double chocolate swirl, add some of your 1 cup pumpkin mixture to some melted white chocolate in addition to the semisweet chocolate. Then alternate your dollops of chocolate over the pumpkin mixture and swirl together.
If you're not a chocolate person, you could use graham cracker crumbs for the crust, omit the chocolate altogether, and just do plain pumpkin cheesecake squares.