Place the dried chipotles in a small cup with enough nearly boiling water to cover; allow to sit 30 minutes to soften.
Rinse shrimp under cold running water, and drain thoroughly.
Heat 2 TBS olive oil in a large heavy skillet and add the shrimps (cautiously, as they may spatter).
Toss the shrimps in the skillet until the shells turn pink, just a minute or two.
Remove the shrimps with a slotted spoon to a bowl and leave aside until cool enough to handle (I put mine in the refrigerator for a few minutes).
Shell and devein shrimp, reserving shells.
Add the shells back to the re-heated skillet along with half of the garlic and toss until the shells begin to brown a bit, just a few minutes.
Add the wine and bring to a boil; reduce heat and simmer 2-3 minutes.
While this is happening, drain the chipotles (RESERVING WATER) and mince them as finely as possible (I don't remove the seeds, but you may choose to do so).
Add enough water to the reserved chipotle water to equal 2 cups; add this to the skillet along with the remaining garlic, chili powder, bay leaf, chili flakes and cumin seeds.
Reduce to a simmer and continue to cook until the liquid has reduced by half; strain, and set the liquid aside.
Wipe the pan clean, then melt the remaining 1 TBS olive oil and butter in it.
Gently saute the onion rings until they are soft and translucent, and just beginning to brown around the edges.
Add the minced chipotles and continue to saute for another 2-3 minutes over moderate heat.
Add a cup of the reserved liquid and simmer until the mixture has reduced and thickened (though it won't really get too thick).
Add the cilantro, if using, and the shrimps and season to taste with pepper; cook over a moderate heat only just until the shrimps are heated through (overcooking will toughen them).
Serve over rice, with lime wedges for squeezing on the side, if desired.