Preheat oven to 450 degrees.
Heat 1/2 cup olive oil in a large saucepan over medium heat. When it is hot, add garlic, oregano, crushed red pepper, capers, and olives and cook until fragrant, about 30 to 45 seconds. Add tomatoes with juice and clam juice, and cook until sauce has thickened slightly, 4 to 6 minutes. Season to taste with salt and pepper.
While tomato sauce is cooking, heat remaining 3 tablespoons olive oil in a large saute pan. Season shrimp with Essence. When oil is hot, add shrimp and cook until just barely pink on both sides, about 2 minutes. Remove pan from heat, and add ouzo. Return pan to heat and carefully shake to ignite alcohol. When flames have died down, season shrimp with salt and pepper. Do not overcook the shrimp; they should not be cooked through at this point.
Spoon tomato sauce into a large casserole or individual gratin dishes. Nestle shrimp in sauce and crumble feta evenly over top. Bake for 10 to 12 minutes or until shrimp are just cooked through and sauce is bubbly.
Remove from oven and serve immediately with warm, crusty bread.