Place chocolate chips and 1 tablespoon heavy whipping cream in a large microwave-safe bowl and heat for 30-45 seconds, or until chips are melted. Remove from microwave and whisk together until smooth. Whisk in sweetened condensed milk, stirring until well combined. Gradually whisk in heavy whipping cream, milk and vanilla extract. Pour mixture into freezer canister of ice cream maker according to your ice maker’s instructions. Before transferring out of freezer canister, stir in 1 1/2 cups brownie pieces. Transfer the ice cream to a freezer-safe container with lid, top with remaining brownie pieces. Cover, place in freezer and allow it to harden for at least 4 hours or overnight.