Keventers serves the best milkshakes out there. I've tried a few flavours from their Kalkaji outlet and trust me they're amazing! And also, BlackJack in Punjabi serves the best Manhattan Chocolate Fudge Shake you'll ever have. Go check them out!
Diggin. The must-haves include Choco Mocha Shake (where sweet and sinful chocolate is combined with the bitter strong flavour of coffee), Strawberry Cheesecake,Berry Blast, and Chocolate Brownie.