Melt chocolate, butter, and cream together
Mix in egg, yolk, brown sugar, flour, vanilla, and salt
Spread brownie base in pan and chill for 1 hour
Blend cream cheese and sugar until smooth
Whisk in eggs, heavy cream, flour, vanilla, and salt
Pour cheesecake batter directly over the cold brownie base
Bake at 440°F for 25 minutes
Reduce temperature to 390°F and bake for 20 minutes
Cool completely, then chill overnight
