Add parsnips, potato and garlic cloves to medium saucepan of boiling salted water. Cook for 15 to 20 min. or until fork tender. Drain well. Transfer back to saucepan. Add cream and salt. Mash until smooth.
Meanwhile, place Swiss chard stems and leaves in saucepan with approx.1 in. (2.5 cm) boiling water. Cover and steam until wilted, 1 to 2 min.
Divide puree onto 4 plates. Top with steamed Swiss chard and cooked trout. Drizzle any remaining butter from steamer bags over top.
Add pinch of ground nutmeg to puree. Substitute 10% half & half cream with 35% whipping cream for added richness. For a smoother puree, process in food processor.