Preheat oven to 325°F (160°C). Line a 9-inch springform pan with parchment and lightly grease the sides.
In a bowl, mix melted butter, sugar, eggs, and vanilla. Stir in cocoa, flour, salt, and baking powder until combined.
Pour brownie batter into prepared pan and smooth the top.
In a separate bowl, beat cream cheese until smooth. Add sugar and mix well.
Beat in eggs one at a time, then add vanilla. Stir in chocolate chips.
Gently pour cheesecake mixture over the brownie base and spread evenly.
Bake for 50–55 minutes, until center is just set. Cool to room temperature, then chill 4–6 hours or overnight.
Before serving, sprinkle extra chocolate chips on top and drizzle with chocolate syrup if desired.