Preheat your oven to 325°F (170°C) and prepare a 9-inch springform pan by spraying it with baking spray that contains flour.
For the crust, in a large bowl, whisk together oats, 3/4 cup of brown sugar, flour, and cinnamon. Then, stir in the melted butter until everything is well combined.
Press the oat mixture into the bottom and three-fourths of the way up the sides of your prepared pan. Bake until fragrant and set, around 15 to 20 minutes. Let cool completely.
Wrap a large piece of heavy-duty foil around the bottom and up the sides of the springform pan to prevent water from seeping in during baking.
For the filling, in the bowl of a stand mixer fitted with the paddle attachment, beat cream cheese, 3/4 cup of brown sugar, and kosher salt at medium speed until smooth and creamy.
Add 1 cup of sour cream and 1 teaspoon of vanilla, beating until fully combined.
Lower the mixer speed to low and start adding eggs one at a time, beating until combined after each addition.
Pour the filling into the cooled crust, spreading it evenly. Place the roasting pan in the oven and add hot water to come about 1 inch up the sides of the springform pan.
Bake until it wobbles slightly when gently shaken and an instant-read thermometer registers 150°F (66°C) to 155°F (68°C), about 1½ hours to 1 hour and 45 minutes.
Increase the oven temperature to 400°F (200°C) and bake the topping mixture until just set, about 5 minutes.
Once cool, carefully remove the foil and bag and refrigerate until set, at least 3 hours or overnight.
For the Butterscotch Sauce, combine all ingredients in a medium saucepan and bring to a boil, whisking until well combined.
Serve with the cheesecake and refrigerate any leftovers in an airtight container for up to 3 days.
