48tablespoonsunsalted butter(6 sticks), cut into 1-inch pieces, at room temperature
⅛teaspoontable salt
Instructions
Make a simple syrup: combine sugar and water in a small saucepan. Bring to a boil over high heat and cook for 3-4 minutes without stirring until syrup reaches 238F on a candy thermometer. While the syrup cooks, whip eggs and egg yolks in a stand mixer with the whisk attachment for 3-4 minutes at medium speed, until pale and light.
Once syrup is ready, reduce mixer speed to low and slowly drizzle the syrup down the side of the bowl into the lightened eggs. (You don't want it to hit the whisk and spatter.) Increase the speed to medium and whip for 6-8 minutes, until mixture is pale, light, fluffy, and cool to the touch. Reduce speed to low and add butter a few chunks at a time. Once all the butter is in the bowl, increase the speed to medium again and whip for 4-5 minutes; the mixture will look curdled but will become smooth with mixing. Add salt and mix to combine.