Combine unsalted butter and 1 cup sugar in large bowl. Using wooden spoon, stir mixture until well combined. Whisk eggs and whipping cream in small bowl to blend. Gradually mix egg mixture into butter mixture. Sift flour, baking powder, salt, ground cardamom and ground nutmeg into medium bowl. Add to butter mixture and mix until soft dough forms. Divide dough into 4 pieces. Wrap each dough piece tightly in plastic; flatten each into disk. Refrigerate dough pieces overnight.
Roll out 1 dough piece on floured work surface to thickness of scant 1/4 inch. Cut dough into 2-inch-wide strips. Cut strips crosswise and diagonally at 3 inch intervals to form diamond shapes. Cut 1 1/2 inch long lengthwise slit in center of each diamond. Gently push one end of one pastry corner through slit and gently pull end back toward its original position. Place on ungreased cookie sheet. Repeat with remaining diamonds. Gather scraps, reroll and cut out additional diamonds. Cover and refrigerate diamonds while rolling and shaping remaining dough disks.
Pour vegetable oil into heavy deep skillet to depth of 2 inches. Heat to 350° F. Add 5 cookies to oil and fry until puffed and golden brown on both sides, turning once, about 3 minutes. Using slotted spoon, transfer to paper towels and drain. Repeat frying of remaining cookies in batches.
Fill large plate with powdered sugar. Roll cookies in powdered sugar to coat. (Cookies can be made 1 week ahead. Store between sheets of waxed paper in air-tight containers at room temperature.)
Makes 3 to 4 dozen