Venice's legendary historic antipasto: fresh sardines lightly floured and fried, layered with sweet, slow-cooked onions simmered in white wine vinegar, plump raisins, and toasted pine nuts.
Dredge the butterflied sardines in flour, shaking off excess. Heat olive oil in a skillet and fry sardines for 2 minutes per side until golden and cooked through. Drain on paper towels and season with salt.
In a clean pan with 3 tbsp olive oil, cook sliced onions over low heat for 20 minutes with a pinch of salt until meltingly soft and translucent without browning. Pour in vinegar and wine, bubbling gently for 5 minutes until vinegar mellows.
Stir drained plump sultanas and toasted pine nuts into the warm onion mixture.
In a ceramic terrine dish, layer fried sardines alternating with the sweet and sour onion mixture, finishing with onions on top. Cover tightly and refrigerate for 24-48 hours before serving at room temperature with polenta.