For the sauce and leeks, sweat shallots in 1 tablespoon of butter until just translucent, about 2 minutes, in a heavy-bottomed saucepan over medium-high heat. Raise heat to high. Add Chardonnay and Champagne vinegar, and reduce to ¼ cup. Add cream and simmer to thicken for another 2 minutes.
Whisk in remaining butter over low heat. When the mixture is smooth, add leeks and braise over lowest possible heat until just cooked through, about 10 minutes. Season with salt and pepper.
For the red snapper, preheat a large nonstick pan over medium-high heat and add oil. Lightly salt the red snapper. When oil begins to shimmer, add red snapper, skin side down. If it begins to buckle, gently flatten with a spatula to ensure even cooking. When skin has crisped, turn the filets and cook until just opaque. Remove fish from the pan before it begins to flake apart.
To serve, arrange a portion of ramps on each plate and spoon sauce over it. Place red snapper on top and finish with a salad of scallion and shiso or other combination of tender spring greens.