Set a large pot or a kettle of water to boil, place a rimmed pan in the bottom rack of the oven. Reduce the oven to 325°F (roughly 160°C)
To a medium bowl, add 24oz (675g) (3 blocks) of full fat cream cheese at room temperature. Use a hand mixer to break down the cream cheese slightly.
Add 3/4 cup (160g) of granulated sugar and 2 Tbsp (20g) of brown sugar and cream until combined. Do your best to not add too much air into the cheesecake batter, just mix until well combined.
Add in 3 large room temperature eggs, one at a time, and mix until combined. Then add 2 tsp of vanilla extract and mix until incorporated.
Switch to a spatula and stir in 3/4 cup (195g) of room temperature sour cream until everything is evenly mixed in.
Pour half of the cheesecake mixture into the cooled graham cracker crust.
Add all of the roasted peaches and about half of the brown sugar crumble directly on top of the cheesecake mixture. Reserve the rest of the crumble for assembly the next day. Top it off with the rest of the cheesecake batter.
Pour the boiling water into the pan at the bottom of the oven. Then place the cheesecake on the rack directly above the pan with the hot water. Remember to place the cheesecake on a tray to avoid leakage.
Bake for 40-50 minutes depending on your oven. For my oven 55 minutes works perfectly. You're looking for a slightly wobbly center. When you stick a toothpick into the center it should come out with some batter on it, as long as it isn't liquid, the cheesecake is done!
When the cheesecake is done baking, turn the oven off and leave the cheesecake in the oven with the door of the oven slightly open for 1 hour. This helps the cheesecake cool down slowly, instead of shocking its temperature, potentially leading to splits.
Once the cheesecake has cooled in the oven for 1 hour, remove it from the oven and allow it to come close to room temperature for another hour or so. Then cover it and place it in the refrigerator to chill for 5 hours or, preferably, overnight.