Preheat oven to 180C/360F and arrange a baking tray in the middle shelf. Grease lightly with olive oil a 12-cup muffin tin.
For the yogurt dip: in a small bowl, mix together yogurt, grated garlic, chopped mint, zest and juice of half lime, and season with sea salt and black pepper to taste. Store in the fridge until ready to use.
Finely mince the broccoli florets, celery and spring onions and add them into a large bowl. Add in mashed sweet potato, salt, cayenne pepper, ginger and chili flakes (optional) and mix all together.
Fold sifted rice and chickpea flour into the mixture and gently mix all ingredients together. The mixture should be dense, if it's too creamy, add a little more flour.
Pour about a full tablespoon of the mixture into each muffin cup. Lightly spray with olive oil the top of each fritter.
Bake in the oven for about 15 min, or until crispy and golden on top.
Allow the fritters to cool slightly, then gently remove them from the muffin tin.
Serve hot or at room temperature with the yogurt dip on the side.