Break up the graham crackers and ginger snaps in a food processor or with a large mortar & pestle.
Add the melted butter and sugar to the crumb, and mix until evenly coated. Pour into the bottom of a springform pan, and press down evenly. Cover with plastic wrap and set in the fridge while you make the filling.
For the filling
Preheat the oven to 315 degrees. In a stand mixer (if you have it, use a hand mixer if not) beat the cream cheese on low for 10 minutes, scraping the sides throughout.
Add the ricotta and white sugar and beat for another 5 minutes until smooth, scraping the sides throughout. Slowly add the evaporated milk while running the mixer on low, until it is all incorporated.
If using a stand mixer, change to the whisking attachment. Add the pumpkin and whisk together on medium speed.
While the mixer is running on medium-low, add the corn starch, vanilla, cinnamon, ginger, clove, nutmeg, and salt. Turn the mixer off, scrape the side, then turn it back on to medium speed for 2-3 minutes until smooth and uniform.
While the mixer is still running, add the eggs one at a time (crack them into a separate bowl first to ensure no shells get added) and whip until evenly incorporated.
Remove the springform pan with the crust from the fridge and discard the plastic wrap. Pour in the batter to within about 1/2in from the top.
Using one solid piece of tin foil, surround the springform pan loosely. Set in a large roasting pan filled with about an inch of water (this is called a water bath).
Bake at 315 for 3 hours. Remove from the oven and let cool for one hour before covering with a cloth or paper towel and setting in the fridge at least over night.
If moisture has gathered on the top after chilling, dab with a paper towel. Cut the cheesecake into 8-16 pieces, depending on the size you want. Serve chilled.