Spray a 9-inch springform pan with nonstick spray. Wrap the bottom and the sides of the pan in 2-3 layers of aluminum foil. Make sure the foil is tight, and several layers thick so no water will get in when you cook the cheesecake in a water bath.
Preheat oven to 350°F.
Combine graham cracker crumbs, melted butter, and sugar in a large bowl, Mix until well combined and sticky.
Dump the mixture into the springform pan, and using your hands or the back of a flat measuring cup, press the crumb mixture into the pan evenly. There should be enough for a thin layer on the bottom of the pan and partially up the sides.
Bake crust in preheated 350°F oven for 7-8 minutes, until just slightly starting to brown. Remove from oven and set aside.
In a large stand mixer, add all 5 blocks of cream cheese. (It will mix best when softened and at room temperature. If you didn't remember to get the cream cheese out early, beat it with the paddle attachment for 5-6 minutes on medium speed to soften it up.)
If you don't have a stand mixer, you can also use a hand-held mixer, it may just take a minute or two longer to get fully softened.
Continue whipping cream cheese with paddle attachment until completely smooth, scraping down the sides as needed.
Add vanilla and sugar. Mix until well incorporated.
Then add the eggs and yolks and continue mixing. (I like to crack the eggs and yolks into a separate bowl first, then pour into the mixing bowl, to ensure no shells get in the smooth filling.)
Slowly pour in the heavy whipping cream and mix until well incorporated. Scrape down the sides as needed and continue mixing until smooth.
Pour filling into prepared crust. Try to level the top as much as possible with a small knife or spatula.
Place springform pan onto a large jellyroll pan or other large pan with edges. Place into oven. Once the pan is in the oven, slowly pour water into the jellyroll pan, about 1 inch high all the way around. Once waterbath is made, close oven door. This water will steam the oven as it cooks, helping it cook more evenly and keep it from cracking. It can also prevent the dairy from curdling. It adds one extra step but it's definitely worth it!
Bake for 1 hour 15 minutes. Once time has elapsed, turn off oven and leave cheesecake in it. Crack the door slightly, propping it open with a wooden spoon if needed. Let cheesecake rest in the oven for another hour.
After hour is up, remove from oven and set on a cooling rack.
Meanwhile, preheat the oven again to 450°F while you prepare the sour cream topping.
In a small bowl mix together the sour cream, powdered sugar, and vanilla with a small whisk or fork.
Gently pour over the cooling cheesecake. Carefully spread the mixture evenly over the top.
Place cheesecake in springform pan back into preheated 450°F oven (no waterbath needed for this). Bake for 5 minutes until sour cream topping is set.
Remove from oven and chill for 3-4 hours until cheesecake is fully set and chilled.
Slice and enjoy!