A classic Italian sauce, tonnato is essentially tuna mayonnaise--only at Bar Tartine in San Francisco, Asian flavors transform it into something better than the original. Use leftover tonnato with any cooked vegetable.
4 ounces albacore tuna, cut into 1/4-in. dice
2 dried shiitake mushrooms
6 garlic cloves, smashed and peeled
3/4 cup grapeseed oil
12 oil-packed anchovy fillets
2 ounces Yukon gold potato (about 1 small), peeled and cut into 1-in. chunks
2 teaspoons Vietnamese or Thai fish sauce
2 large egg yolks
1 tablespoon lemon juice
Salt and pepper
How to Make It
In a small saucepan over very low heat, combine tuna, mushrooms, garlic, and grapeseed oil. Drain any oil from anchovies into pan, then set aside anchovy fillets. Cook, uncovered, until garlic is tender enough to be easily pierced with a skewer, about 30 minutes. Remove from heat, transfer to a bowl, and chill until cold, about 1 hour. Discard mushrooms (or save for another use, like soup).
Meanwhile, put potato in a small saucepan, add enough water to cover, and bring to a simmer over medium heat. Cook until tender enough to be easily pierced with a skewer, 10 to 15 minutes. Drain well and set aside.
Strain chilled tuna mixture, reserving oil. Put tuna mixture in a food processor with cooked potato, anchovies, fish sauce, egg yolks, and lemon juice and purée, scraping down bowl occasionally, until smooth, about 1 minute. With motor running, slowly pour in strained oil and whirl just until very thick (if you overprocess, the sauce will break). Season with salt and pepper.