How to Make It
Preheat oven to 425°F. Place Romanesco on a parchment paper–lined rimmed baking sheet. Brush each head with 1 tablespoon oil, and sprinkle with salt and pepper. Roast until outer leaves are crisp and Romanesco is just tender and browned, about 45 minutes.
Toss bread cubes with remaining 2 tablespoons oil, salt, and pepper. Spread on a parchment-lined baking sheet, and bake at 425°F until toasted and dry, 8 to 10 minutes. Let cool.
Place toasted bread in a large ziplock plastic bag. Seal bag, and crush with a rolling pin until coarse breadcrumbs form. (Alternatively, you can pulse toasted bread in a food processor.) Place breadcrumbs in a bowl, and add 1/4 cup Parmesan, anchovies, zest, and garlic; stir to combine.
Transfer Romanesco heads to a serving platter, and drizzle with oil. Sprinkle with breadcrumb mixture and additional Parmesan. Cut Romanesco into wedges and serve.