Place a medium-sized pot of water over medium heat and bring to a simmer. 

Wash the fruit, slice any larger fruit or berries and divide between 6 dessert bowls.

In a large mixing bowl that will easily fit over the pot of simmering water, combine sugar and egg yolks. Whisk together to create a light, butter-yellow mixture, about 1 minute. Pour in the sparkling wine and sea salt and continue to whisk. The mixture will start to aerate and will become quite fluffy. Place the bowl over the pot of simmering water and whisk continuously for 5–7 minutes. (It’s most effective to whisk in a circular motion up and over, adding even more air into the custard.) 

The custard is done when it is stiff enough to hold a soft peak for 6–8 seconds. Remove the bowl from the pot of water and whisk 3–4 more times, as the custard will continue to set. Spoon the custard over the bowls of fruit and serve immediately. 

This custard will store in an airtight container in the fridge overnight, although it is best served immediately. If you do need it to hold, fold one cup of stiffly whipped cream into the custard. 

Note: Using farm-fresh eggs or unpasteurized eggs may increase the risk of food-borne illness.