Place red potatoes in large pot. Fill with water until potatoes are covered. Boil until soft. Remove from pot and mash potatoes in bowl.
Blend in the parsley, cilantro, garlic, eggs, cumin, cayenne, pepper and salt. Mix thoroughly and form little 2-3 inch long rectangular patties.
Scale the sardines, remove the tails and heads, and split them open down the belly. Empty them and remove the backbone. Salt them for 10 minutes, then rinse, drain and dry them.
Spread and lay a sardine flat, skin side down. Place a potato patty on it, then top with another spread open sardine, this time skin side up, creating a "sardine sandwich." Repeat the process until all the sardines are used.
In a large frying pan, heat 1 cup of oil to medium high.
Dredge the stuffed sardines into flour and tap excess flour off.
When the oil is hot, carefully place the stuffed sardines in the frying pan and deep fry until the skin starts to become crispy and golden. Remove from heat and place on rack.