Preheat oven to 400 °F (200 °C).
Cut stem off garlic heads to expose cloves. Wrap with foil and roast for about 1 hour until very soft. Let cool slightly. Squeeze out garlic cloves from each head and mash in canola oil with fork. Stir in parsley and pepper; set aside.
To prepare lentil mash: spray nonstick skillet with canola oil cooking spray and over medium heat, add lentils, tomatoes, garlic and thyme. Cook for 5 minutes; mash slightly. Stir in broth and keep warm.
Spray fish fillets with canola oil cooking spray and sprinkle with curry powder and parsley. Preheat oven to 350 °F (180 °C).
In nonstick, ovenproof skillet over medium-high heat, sear fish on both sides. Spread roasted garlic mixture on top of fillets and place in oven for about 5 minutes or until fish flakes easily when tested.
Spoon lentil mixture into shallow bowl and top with fish fillets.
Recipe Tip If using canned lentils, rinse and drain them first. Also, you can roast multiple garlic heads ahead of time and freeze them for later use. Simply thaw before using in the recipe.