Smashed avocado with crispy chicken, pickled onions & tortillas

Name: Smashed avocado with crispy chicken, pickled onions & tortillas
Prep time: 50 min
Cook time: 25 min
Total time: 1 h 15 min
Cuisine: American
Ingredients: 2 large, very ripe avocados; juice 1 lemon; 8 seeded soft tortillas , or your favourite flatbreads, warmed; small bunch coriander , to serve; 1 large red onion , very thinly sliced; 100ml red wine vinegar; 4 tbsp caster sugar; 4 skinless chicken breasts , each cut into 3-4 chunky strips; 284ml pot buttermilk; 85g polenta or cornmeal; 85g plain flour; 1 tbsp sesame seed; 1 tbsp sweet paprika; ½ tsp cayenne pepper; 2 pinches ground cinnamon; 1 tsp garlic salt (or normal salt); sunflower oil , for shallow-frying