Prepare the blackening spice. Put all listed ingredients into a coffee grinder and grind for approximately 1 minute. Set aside.
Preheat oven to 350 degrees Portion the grouper fillet into 4 equal portions, leaving the skin on. Place the fillet skin-side down on a plate and generously rub the blackening spice onto the flesh. Set aside.
Roast the fingerling potatoes in oven for 15 minutes or until they are fork tender. Peel and blanch the asparagus in salted boiling water until al dente. Saute the morels with the spring peas and butter until tender. Blanch, shock and puree the watercress in a blender with the cream and 2 tablespoons grapeseed oil for a fine puree.
Heat the remaining 2 tablespoons grapeseed oil until it smokes and carefully place the grouper flesh side down and blacken the fish. Finish in the oven for 10 minutes.
To finish the dish, reheat the asparagus on the grill. Bring the watercress cream to a simmer. Reheat the morels and peas. Reheat the fingerling potatoes. Place the asparagus on the plate, place the morels and peas on top of the asparagus. Place the fingerlings next to the vegetables. Place the grouper on the side of the vegetables and sauce. Garnish with a few watercress leaves.