In a mixing bowl, dissolve the gelatin with the cold water and then stir in the boiling water.
Set aside.
Remove the milk from the heat and stir in the dissolved gelatin.
Slowly blend this mixture into the potatoes until they are thickly textured.
Line a 9 by 4-inch loaf pan (or other shaped pan, as desired) with plastic wrap; the wrap should extend over the edges of the pan by a couple of inches on all sides.
Place one third of the potato mixture in the bottom of the pan and spread out evenly.
Add a layer of half of the hearts of palm and then another layer of one third of the potato mixture.
Place slices on a baking sheet and bake for 5 to 8 minutes, or until browned.
Meanwhile, unfold the top covering of plastic wrap from the terrine, and gently invert the loaf pan on a serving platter, running a knife around the inside edge if necessary.
Carefully remove the plastic wrap and cut the terrine into slices.
Garnish with the coconut, goat cheese, and greens and serve with the herb toast and vinaigrette on the side.