Pound the pork cutlets until they are very thin (1/8"), being careful not to tear the meat.
Stir the wine, garlic, siracha, bay leaves, vinegar, paprika, and salt. Add the pork to a shallow pan and pour the marinade over top, and submerge the meat. Refrigerate for 1-1/2 hours, tossing the meat several times.
Heat a large skillet until hot, then add the lard. Fry the cutlets (reserve the marinade) quickly just until cooked through, about a minute per side, adding more lard as needed. Transfer the cooked meat to plate, and set aside.
Slice the onions into 1/2 inch slices. Separate the rings then add them to the skillet and saute until softened. Discard the bay leaves, then pour the reserved marinade into the pan with the onions, and heat for 5 minutes. Add the pork back into the skillet, reduce the heat to low, and simmer for 5 minutes.
Slice the buns and spoon some of the sauce & onions over half of each bun, then pile with meat.