Preheat oven to 325°F (160°C). Line a 9-inch springform pan with parchment. Wrap the outside with two layers of foil to prevent leaks during the water bath.
Mix crushed graham crackers, melted butter, and sugar until sandy. Press into the pan base. Bake for 10 minutes, then let it cool.
Beat cream cheese until smooth (2–3 mins). Add sugar and vanilla; beat until fluffy.
Add eggs one at a time, mixing gently. Stir in sour cream and flour just until blended—don’t overmix.
Pour filling over the crust and smooth the top.
Place the pan in a roasting tray. Add hot water halfway up the sides. Bake 55–65 minutes until set around edges but center still jiggles.
Turn off oven, crack the door, and let it sit for 1 hour. Cool to room temp, then chill for at least 6 hours or overnight.
Simmer blueberries, sugar, and lemon juice until berries burst (5–7 mins). Stir in cornstarch slurry; cook 2 more minutes until thick and glossy. Cool.
Spread blueberry topping over chilled cheesecake. Slice with a hot, clean knife. Serve and enjoy!