In a small bowl, combine half of garlic, vinegar, 3 tsp thyme, pepper, Dijon and oil. Rub mixture on all sides of steaks, transfer to resealable container, cover and refrigerate for 4 to 24 hours.
Heat a medium saucepan on medium-high and mist with cooking spray. Add shallots and sauté, stirring frequently, until soft and light golden, about 2 minutes. Stir in wine, broth and 3 cups blackberries and bring to a boil. Reduce heat to medium and simmer, stirring occasionally, for 10 minutes, until berries are very soft and liquid is reduced by about half. Remove from heat.
Over a small bowl, strain blackberry mixture through a fine mesh sieve, gently pressing on solids with a ladle to extract juice from berries; discard solids. Rinse saucepan; return blackberry sauce to pan over low heat, cover and keep warm.
Heat a grill or grill pan on medium-high and lightly brush with oil. In a large bowl, combine remaining half of garlic, 1 tsp thyme and lemon juice. Add fennel and toss to combine. Mist with cooking spray and toss gently to coat. Season with sea salt and pepper, to taste. Add fennel to grill and cook,turning once, until golden brown and lightly charred on the edges, 8 to 10 minutes. Set aside and cover to keep warm.
Season steaks with kosher salt and grill for about 3 minutes per side, until an instant-read thermometer registers 145°F when inserted in center of steak. Let steak rest for 3 minutes. Return sauce to medium heat and stir in butter until melted. (NOTE:Do not use oil or pre-melted butter, as it will not emulsify.) Divide steak and fennel among serving plates. Top with blackberry sauce and remaining blackberries, dividing evenly.
This spice-rubbed steak on the grill is special enough. But here, a good thing gets even better with a bold tomato and pepper sauce reminiscent of gazpacho. For a change of pace, try substituting chicken, pork chops or even shrimp for the beef.
Butterflied flank steak rolled around a flavorful kale and feta filling makes an impressive presentation for dinner guests, and only you'll know how easy it was to pull off. Searing the rolls before simmering them in a white wine and tomato sauce ensures a juicy result.