准备

Make the flavor base:

• In a food processor, combine the raspberries, blackberries, 1/4 cup of the sugar, the lemon juice, and salt. Purée until smooth. Pass the purée through a fine sieve; discard the contents of the sieve. Set the purée aside.
• Choose a medium stainless-steel bowl that can rest just inside a medium saucepan. Pour about 1 inch of water in the saucepan and bring to a boil. Choose a large bowl that’s big enough for the medium bowl to fit inside it. Fill the large bowl with ice water; set aside.
• Put the egg yolks, 1/4 cup of the sugar, and 1/2 cup of the berry purée in the medium bowl. When the water in the saucepan boils, reduce the heat to a gentle simmer, and set the bowl with the berry mixture on the saucepan. Whisk until the mixture reaches 140°F on an instantread thermometer. Turn off the heat but leave the bowl over the water and continue whisking for 31/2 minutes. (If the temperature reaches 150°F, remove the bowl from the water, whisk until the temperature drops to 145°F, and then return the bowl to the water bath to continue whisking.) Remove the bowl from the saucepan, stir in the remaining berry purée, and set the medium bowl into the ice bath to cool. Don’t pour the hot water out of the saucepan.

Bloom and dissolve the gelatin:

• 将1/4杯冷水倒入一个小的耐热奶油杯中；将明胶均匀地撒在杯中的水中。静置约5分钟。将明胶与热水一起放入锅中，将明胶混合物搅拌至明胶融化，并变得半透明，大约2分钟。
• 明胶融化后，将其搅拌到浆果混合物中。偶尔搅拌，直到混合物冷却至50°至55°F并略微变厚。

击败蛋清和奶油：

• 在一个干燥的，无油脂的碗中，用手动搅拌机（确保搅拌器干燥，也没有油脂）以低速打击蛋清，直到泡沫为止。加入牙垢霜（有助于稳定泡沫）。将速度提高到中高。打直到白色变不透明，开始变稠，然后看起来泡沫，1-1/2分钟。逐渐击中剩余的1/4杯糖。继续跳动，直到白色看起来厚而光泽（但不干燥），类似于厚厚的奶油，并形成中等峰，约3分钟。

  

• 在一个单独的碗中（这次无需清洁搅拌器），将奶油打成大约2分钟的奶油直至柔软的峰形成。

Assemble the mousse:

• 将几勺打的蛋清搅打到浆果混合物中，以减轻它。将冰和水从冰浴碗中倒出；干碗。将淡淡的浆果混合物倒入冷碗中。

  

• 刮上剩余的蛋清和奶油nd fold gently with a rubber spatula until just combined. Spoon the mousse into individual glasses, into a 6-cup bowl, or into individual ramekins. Refrigerate, covered, until firm, at least 4 hours but no longer than 24 hours. Garnish with reserved whole berries and sprigs of mint, if you like.