Bring milk and cream to boil in a 12 inch to 14 inch saute pan. Add blood orange zest and 1/4 cup sugar. Stir through and lower heat to medium simmer. Meanwhile, whisk whites to form soft peaks. Add 1/4 cup sugar and blood orange juice and whisk to stiff peaks. Scoop 1 large tablespoon of egg white mixture and place on to simmering milk. Place 3 or 4 at a time on to milk and cook for 2 minutes per side, flipping carefully with a large kitchen spoon. Remove each sciumetta and place in a shallow bowl. DO NOT BOIL MILK.
In a heavy bottomed enamel covered saucepan, whisk egg yolks with remaining sugar until pale ribbon stage. Add warm poaching milk to yolk mixture and cook carefully over low heat to thicken CAREFULLY. When as thick as heavy cream, remove to bowl over ice bath and whisk until cool. Pour cooked custard into bowl and top with sciumette. Dust with cocoa and serve.