For the Pickled Red Onions
Simmer all ingredients, uncovered, over medium heat until onions are tender and liquid has evaporated.
Pickled red onions will keep for up to 6 weeks, refrigerated
For the Maple Toasted Pecans
Preheat oven to 175°C and line a baking tray with parchment paper. Toss pecans with maple syrup and black pepper to coat.
Spread pecans on prepared tray and bake for 10 to 12 minutes, without stirring, until toasted. Once cooled the maple syrup will caramelize onto pecans.
Store pecans in an airtight container for up to a month.
For the Fiddlehead Salad
For vinaigrette, whisk lemon juice, shallot and Dijon to blend. Gradually whisk in grapeseed or canola oil until incorporated, then whisk in water. Season to taste and stir in chives.
For fiddleheads, trim off stem end and wash thoroughly, rubbing gently between your fingers. Drain well. Bring a pot of water to a boil and salt generously.
Blanch fiddleheads until tender, about 5 minutes (tasting is the best way to judge). Drain fiddleheads and shock in ice water to halt cooking. Drain and chill until ready to serve.
To assemble salad, arrange radicchio on a platter. Toss fiddleheads with vinaigrette and arrange on platter.
Spoon pickled red onions over and top with maple toasted pecans. Serve immediately.