1
Preheat the oven to 375°F.
2
In a large stockpot, place the potatoes and a generous pinch of salt. Cover with cold water and bring to a simmer. Cook at a simmer until the potatoes are fork-tender, about 15 minutes. Drain the potatoes and return to the pot. Add the butter, milk, buttermilk, salt and pepper. Mash until smooth.
3
Pat the salmon dry, season with salt and pepper and arrange on a baking sheet. Roast for 12-15 minutes, until cooked through.
4
Combine all of the relish ingredients in a bowl.
5
To serve, divide the mashed potatoes and salmon between plates. Top with broccoli and relish.