To make the streusel topping, combine brown sugar, flour, oats, and salt. Work in the butter, mixing until coarse crumbs form. Cover and refrigerate until ready to use.
To make the caramel drizzle, In a small pot over medium heat, bring brown sugar, butter, and cream to a gentle boil and cook until thickened, 2-4 minutes, stirring constantly. Remove from heat; add vanilla extract.