Step 1 In a large bowl, sift together the flour and baking powder. Using a pastry cutter or fork, cut the cream cheese into the flour mixture, and then work in the butter. Add the whipping cream and vanilla and mix to make a smooth dough, being careful not to overmix.
Step 2 Form the mixture into small walnut-size balls (about 2 teaspoons dough per ball). They may be a bit sticky, but don't add flour. Put them into a bowl, cover with plastic, and chill overnight.
Step 3In the bowl of a food processor, combine the walnuts, sugar, raisins, grated lemon peel and beaten egg white. Pulse to finely grind.
Step 4Heat the oven to 400 degrees. Roll out the balls on a well-floured board to make 4-by-3-inch rectangles. Take a generous teaspoon of the nut mixture and form it into a pencil-shaped log, almost the length of the cookie dough. Place it along the edge of one of the wide sides of a rectangle and roll up the pastry around it. Form the pastry into a crescent shape and turn the ends under, sealing them closed. Continue this way until all balls are made into crescents. The balls should remain cool. Should they become warm, keep them in the refrigerator until you are ready to make the next ball.
Step 5Bake until set, 15 to 20 minutes. Dust with powdered sugar while still warm.