If using brown or white rice, grind it in a coffee grinder until finely ground or use any flour. (Rice flour works as well.)
Mash plantains with a potato masher or spoon until puree, or use a food processor to blend. Put it in a medium bowl.
Add the rice, baking powder, salt, garlic, ginger, and cayenne pepper to the mashed plantains. Stir in onions, green onions, and parsley until fully combined.
Adjust seasonings to taste; you may want to fry one up first to do a test taste.
Heat oil to 350℉ (180℃) degrees in a skillet or saucepan. You can also use the oil test by dropping a 1-inch square of bread into the oil. If it takes 60 seconds to brown, then the oil is at around 350℉ (180℃).
Using your hands, roll about a tablespoon of mixture in the palm of your hand into a little bite-size ball. Or use a spoon to scoop it out directly into the hot oil.
Carefully place the batter by spoonfuls into the hot oil and fry for 3-4 minutes or until the fritters are crisp and golden brown. You may need to do this in batches, so repeat with the rest of the batter until it is used up.
Remove the fritters from the pan with a slotted spoon and drain them on paper towels to remove excess oil.