1. Position rack in the center of the oven and preheat to 350¡F.

2. Place the biscotti in the bowl of the food processor fitted with the metal chopping blade.

3. Pulse the machine at 3 to 4 second intervals until the biscotti are finely ground.

4. Set aside.

5. In the 4 1/2-quart bowl of a heavy-duty electric mixer (such as Kitchen Aid) using the paddle attachment, cream the butter and sugar together on medium-high speed for 3 to 4 minutes, until light and creamy.

6. Add flour and the biscotti crumbs to the creamed mixture and blend for 30 seconds, until fully incorporated.

7. Press the mixture evenly into the bottom of a 9-inch springform pan. Bake the crust until it's golden brown, approximately 20 minutes.

8. Remove the pan from the oven, place on a wire rack and allow to cool completely.

9. Make the cheesecake: In the 4 1/2-quart bowl of a heavy-duty electric mixer (such as Kitchen Aid), using the paddle attachment, beat the cream cheese on medium speed until light and smooth.

10. Add the mascarpone and sugar and continue to beat on medium speed until well blended, approximately 2 minutes.

11. Take care NOT to whip much air into the cheese mixture (this will cause the cake to fall when cooling).

12. With the mixer on medium speed add the eggs one at a time, scraping down the side of the bowl after each addition.

13. Blend in the lemon zest and lemon juice.

14. Pour the mixture on top of the cooled crust.

15. Wrap the 9-inch springform pan with aluminum covering the bottom and sides so no water might leak through.

16. Place the springform pan inside a metal roasting pan. Fill the roasting pan with water, being careful not to splash any of the water into the cheesecake mixture, until it comes approximately 1/4 of the way up the side of the springform pan. Bake for approximately one hour, until the cake has set and the top is golden brown.

17. Remove the cake from the oven and from the water bath.

18. Place it on a wire rack and allow to cool slightly.

19. Refrigerate the cake until completely cooled, 6 hours or overnight.

20. Garnish the cake: Place a rack in the center of the oven and preheat to 350¡F.

21. Place the sliced almonds on a baking sheet and toast them in the oven for approximately 10 minutes, until golden brown and fragrant.

22. Remove the nuts from the oven and place the pan on a wire rack to cool.

23. Set aside.

24. Loosen the cake by running a knife between the cake and the side of the pan. Remove the cake from the pan and press the sliced almonds around the sides of the cake.

25. Slice and serve.