Sprinkle salmon with 1/4 tsp. each salt and pepper. Heat oil in a large, heavy nonstick frying pan over medium-high heat until it ripples. Add salmon (skin side down if using fillets). Reduce heat to medium-low and cook without moving fish until it is about half-cooked through, 5 to 7 minutes. Carefully turn fish over and cook until lightly browned, 2 to 4 minutes more for medium-rare to medium. Transfer fish to a plate (skin side up for fillets); tent with foil.
Increase heat to medium-high and cook bacon, stirring, until crisp, 3 to 4 minutes. Transfer to paper towels to drain. Discard all but 1 tsp. fat from pan.
Return pan to heat, add shallot, and sauté 1 minute. Add crème fraîche, snap peas, and half the mint; cook, tossing peas, just until they're glossy and bright green, 1 to 2 minutes. Add salt and pepper to taste.
Spoon snap peas onto a rimmed platter, set salmon on top (skin side down for fillets), and sprinkle with bacon and remaining mint.