Rinse the sea breams with cold water and pat dry inside and out. Lightly season inside and out with salt and pepper. Place a sprig of parsley inside each fish.
Preheat the oven to 220°C (428°F).
Heat the olive oil in a flat baking dish over medium heat. Add the chopped shallots and cook until softened and lightly golden, about 2-3 minutes. Remove half of the cooked shallots, mix with the breadcrumbs, and set aside.
Add the crushed garlic cloves, chopped anchovy fillets, capers, tomato paste, and chopped herbs to the remaining shallots in the pan. Season with a pinch of salt. Heat while stirring for about 2 minutes.
Place the prepared sea breams in the pan, nestled in the sauce.
Sprinkle the breadcrumb and shallot mixture over the fish. Cut the butter into small flakes and scatter over the top.
Bake in the preheated oven for 12-15 minutes until the fish is cooked through.