Combine first 10 ingredients except the flank steak. Place flank steak in a hotel pan and pour the marinade over it, turning to coat. Cover and refrigerate at least 2 hours or up to overnight. Grill over high heat to desired degree of doneness. Let rest for a minimum of 5 minutes. Place on a cutting board and slice against the grain.
Garlic Flavoured Oil
Place ingredients in a saucepan and warm oil to about 200°F (95°C). Remove from heat and let steep for 1 hour. Strain garlic using a kitchen sieve or cheesecloth. Store as you would normally store oils. Use as desired.
Black Bean Vinaigrette
Combine cumin and garlic oil in appropriate sized saucepan. Heat over medium heat for 3-4 minutes to lightly toast seeds. Remove from heat. Add olive oil vinegar cilantro peppers onions and beans. Season with salt and pepper to taste. Place mixture in blender and pulse a few times to lightly blend ingredients. Serve as a side dish or drizzle over Grilled Flank Steak.
