Using a mortar and pestle, crush 2 tbsp pecans. In a small bowl, combine crushed pecans, graham cracker crumbs and butter until evenly moist. Press into the bottom and halfway up the sides of the prepared pan.
In food processor, process cream cheese and sugar until smooth, scraping down the sides of the bowl as needed. With the motor running, add eggs through the feed tube and process until smooth. Add flour, cottage cheese, lemon zest, lemon juice and vanilla; process for 2 minutes or until smooth and creamy. Pour batter into the pan.
Add 2 cups water (or the amount required by your cooker to reach pressure) to the pressure cooker and place the steam rack in the pot. Place the pan on the rack. Close and lock the lid. Cook on high pressure for 25 minutes. Let stand, covered, until the float valve drops down. Check to make sure a tester inserted in the center of the cheesecake comes out clean; if more cooking time is needed, reset to high pressure for 5 minutes. Carefully remove pan and rack; let stand on rack for 1 hour. Remove the edges ring of the pan, cover and refrigerate cheesecake for at least 6 hours or up to 2 days.
Sprinkle remaining chopped pecans and toffee bits on top of the cheesecake. Heat caramel ice cream topping in the microwave or in a small saucepan, 30 seconds or until just softened. Drizzle caramel on top of the nuts and toffee.
Tip* Make sure not to overprocess the mixture in step 2, or the cheesecake will become too firm and not as creamy.
Variation* Instead of the graham cracker crumbs, use crushed vanilla wafers, chocolate wafers or shortbread cookies.