Tonnato Sliders

• 1/4 cup olive oil
• 2 tablespoons unsalted butter, divided
• 1 small yellow onion, chopped
• 1 small fennel bulb, chopped
• handful of spring radishes (5 or so), trimmed and chopped
• 1 teaspoon hot pepper flakes, or to taste
• generous pinch of caraway seeds
• 6 garlic cloves, chopped (remove and discard any green shoots)
• 9 anchovy fillets
• big handful of Italian parsley leaves, chopped (to yield a 1/4 cup or so)
• 3 6-8 oz cans good-quality tuna in olive oil, darined and chopped, oil reserved
• 1/2 cup dry white wine
• 1/4 cup capers, drained and rinsed
• 1/2 cup mayonnaise or aioli
• 2 tablespoons wine vinegar or lemon juice
• 2 tablespoons water
• salt and freshly ground pepper, to taste

1. Heat the olive oil and 1 tbsp of the butter in a large skillet over medium-low heat. Add onions, fennel, and radishes, and saute until tender and translucent. Add pepper flakes, caraway, garlic, and anchovies, and continue sauteing until anchovies have dissolved, then stir in the tuna, mashing with the back of a wooden spoon to break up any large chunks. Raise the heat to high and add the wine. Cook until almost all evaporated, then lower the heat and stir in the capers and the parsley. Stir in the remaining tbsp of butter and remove the pan from heat. Let the mixture cool completely.
2. Transfer half of the skillet mixture to a food processor with the mayonnaise (or aioli), vinegar (or lemon juice), and water. Measure out and add 2 tbsp of the tuna oil, discarding the remainder. Pulse until you achieve a pasty consistency. Transfer to a mixing bowl and lightly mix with the remaining skillet mixture. Refrigerate several hours or overnight.
3. When you are ready to cook, form the mixture into patties of roughly equal size and heft. I think slider-size is ideal, but feel free to go big. Heat a large non-stick skillet and slick with a light coat of olive oil. When it shimmers, add the patties in batches, taking care not to overcrowd. Pan-fry until browned, then flip and cook until heated through. Serve on mini-brioche buns, or better yet, mini croissants, perhaps with some arugula or watercress and a little cheddar melted over. (Do this open-faced for tuna melt-style.)

olive oil, unsalted butter, yellow onion, fennel bulb, handful of spring radishes, hot pepper, generous, garlic, anchovy, handful of italian parsley leaves, olive oil, white wine, capers, mayonnaise, wine vinegar, water, salt

Taken from food52.com/recipes/29358-tonnato-sliders (may not work)