in a saucepan, over medium-low heat, combine 1/2 cup of the oil and the shallots. simmer until the shallots are light golden brown, about 12 minutes. transfer to a bowl and stir in capers, vinegar, 1/4 tspn salt and 1/4 tspn pepper, set aside. heat 1 tbsp of the oil in a large skillet over medium - high heat. season the fish with 1/4 tspn salt and 1/4 tspn pepper and cook until opaque, about 4 mins each side. divide among plates. wipe out the skillet and heat the remaining oil over medium heat. add the spinach, 1/2 tspn salt and 1/4 tspn pepper. cook stirring until wilted, 2 to 3 mins. serve with striped bass drizzling the vinaigrette over the top.