To make the smashed avo cream, place the avocado and lime juice in a medium bowl. Use a fork to mash. Season. Add the sour cream and stir to combine. Cover with plastic wrap and place in the fridge.
Use a small serrated knife to cut down the side of the corn to release kernels. Place the corn kernels, polenta, flour, haloumi and 1 tsp Mexican seasoning in a large bowl. Whisk the eggs and buttermilk in a jug. Add to the flour mixture in the bowl. Stir to combine.
Add enough vegetable oil to a large saucepan to come one-third of the way up the side of the pan. Heat over medium-high heat until oil reaches 180°C (when oil is ready, a cube of bread turns golden brown in 15 secs). Use a metal spoon to carefully lower three to four 1-tbs portions of the batter into the oil. Cook for 3 mins or until golden. Use a slotted spoon to transfer fritters to a plate lined with paper towel. Repeat with the remaining batter to make 24 fritters.
Transfer the fritters to a serving bowl. Season. Sprinkle with the remaining Mexican seasoning. Serve with the smashed avo cream. Serve with coriander sprigs, spring onion curls and lime wedges.