Preheat oven to 200C. Heat 20ml oil in a saucepan over low heat, add shallot and garlic and cook until tender (4-5 minutes). Add beans and stock, cook until reduced by half and warmed through (3-4 minutes). Pulse in a food processor until coarsely chopped, return to pan, stir through half the lemon rind and juice, season to taste, keep warm.
Meanwhile, place trout, skin-side up, on a lightly oiled oven tray. Drizzle with 20ml olive oil and a little lemon juice, roast until cooked to your liking (5-6 minutes for medium-rare).
Thinly shave fennel on a mandolin, place in iced acidulated water until crisp (1-2 minutes), drain well. Combine in a bowl with capers, parsley and reserved fronds. Add remaining olive oil, rind and juice, season to taste, toss to combine, and serve with roast trout and white bean purée.
Recipe from August 2009 issue of Australian Gourmet Traveller.