This recipe is easiest to do when using a sous vide device -- either a self-contained insulated box called a water oven or a stick-style water circulator along with a pot of your choice. You can also follow our instructions below for using a small (8- to 12-quart) cooler and a digital thermometer. We’ve tested this recipe using both gram measurements and traditional U.S. volume and weight measurements, so you can pick the one that works best for you. This recipe safely achieves pasteurization (144 degrees Fahrenheit/62.2 degrees Celsius for at least 6 minutes) and then continues to heat the yolks to create a sauce with the ideal texture. Store-bought, in-shell, pasteurized eggs can also be used without any changes to the recipe. The cooking time depends on the number of yolks, so this recipe cannot be scaled up or down without making adjustments. Don’t discard the whites—save them to make angel food cake or meringue cookies or freeze them for later. This sauce can be refrigerated for up to one week.
1. Use sous vide device to heat water bath to 149 degrees F/65 degrees C. Alternatively, fill 8- to 12-quart cooler halfway with boiling water; close lid and set aside.
2. Using spatula or ladle, push yolks through fine-mesh strainer into medium bowl; gently whisk yolks and salt until just smooth (do not overwhisk). Pour mixture into 1-quart double-zipper zipper-lock bag; seal zipper, leaving ¼-inch opening on 1 end. Holding bag near opening, allow bag to lie flat on counter so that egg mixture fills bag and pushes air out opening. Seal bag fully.
3. If using cooler, add cold water until water in cooler registers 151 degrees F/66 degrees C. Gently lower bag into water bath or cooler, allowing any remaining air bubbles to rise to top of bag (do not let go of bag). Reopen 1 corner of zipper, release remaining air pocket, and seal bag fully. Release bag into water bath or cooler and cook for 32 minutes. If using cooler, stir in boiling water as necessary to maintain water temperature of 149 degrees F/65 degrees C; keep cooler lid closed when not adding water.
4. Meanwhile, combine ice and water in large bowl; set aside.
5. Remove bag from water bath or cooler and immediately transfer to ice bath; let chill until cold to touch, at least 10 minutes. Transfer sauce to airtight container or squeeze bottle and refrigerate until ready to use.
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"Vegetables are perishable, so we don't have any indication of what they looked like 500 years ago," says James Nienhuis, a professor in the Department of Horticulture at the University of Wisconsin.