In small sauce pan over medium heat, warm canola oil. Add Serrano chili halves and toast gently, about 30 seconds per side. Place chilies in bowl and cover with 1 cup boiling water. Allow to sit for 10 minutes or until softened. Drain, reserving soaking water.
Make mole sauce by placing in bowl of food processor 4 charred tomatillo pieces, charred tomato pieces, peanuts, sesame seeds, garlic, raisins, cinnamon, ½ teaspoon black pepper, cloves and chocolate. Add chilies and ¾ cup soaking water. Blend until smooth and set aside.
Season chicken legs with salt and remaining ¼ teaspoon black pepper. In large lidded sauté pan, warm vegetable oil over medium high heat. Add chicken legs, skin-side-down and cook, turning, until well-browned, about 8 minutes per side. Remove chicken from pan and set aside.
Transfer tomato and tomatillo mixture to same pan; cook over low heat for 10 minutes. Return chicken to pan, add chicken stock and bring to a boil. Cover, reduce heat to medium low and simmer 50 minutes.
Remove chicken from sauce and cool slightly. Remove chicken meat from bones, chop fine and return meat to sauce. Add sugar. Keep mole warm until needed.
While chicken is cooking, prepare salsa by combining in medium bowl pineapple, diced tomatillo, cilantro, lime juice, olive oil, salt and pepper. Mix well, cover and chill.
Slice polenta according to package directions, making approximately 10 one-half inch slices. Warm in 375°F oven or on hot skillet for 15 minutes.
To serve, place 2 polenta slices on each plate. Top with heaping tablespoon of chicken mole and 1 teaspoon salsa.