Fit the souffle dish, or dishes, with doubled bands of foil, brushed with vegetable oil. The foil should extend about 3 inches above the rim of the dish(es).
Using a double-boiler, or heat-safe bowl over saucepan with simmering water, melt both chocolates, stirring occasionally, until smooth.
In a separate bowl, beat egg YOLKS, until they are thick and pale.
In a small saucepan, combine the raspberry juice with 1 1/2 T of sugar. Bring to a simmer, then add to the egg yolks in a very slow stream, beating constantly. If you add too quickly, it will cook the yolks. Continue to beat mixture for 1 minute.
Add yolk/raspberry mixture to chocolate in the same manner as above.
In a large bowl, beat egg WHITES until frothy, then add the cream of tartar. Continue to beat until the whites hold soft peaks. Add the 1/3 cu sugar a little at a time and continue beating until whites have stiff, glossy peaks.
In a chilled bowl, beat the cream until is has stiff peaks.
Stir 1/4 of the whites mixture into the chocolate mixture, then fold in the remaining whites. Just before they are fully incorporated, fold in the whipped cream.
Spoon mixture into the prepared souffle dish(es), cover loosely and chill for at least 3 hours or until set. Remove collar just before serving.
Can be made up to 1 day in advance.