Line two baking sheets with parchment paper; set aside. In large mixing bowl beat butter on medium 30 seconds. Add sugar; beat well. Beat in egg, vanilla, baking soda, and salt. Beat in as much flour as you can; stir in remaining by hand.
Divide dough in half. Shape each half in a 7-inch log about 1-1/2 inches in diameter. (For small cookies, shape dough in 10-inch logs about 1 inch in diameter). Wrap in plastic wrap or waxed paper. Freeze 2 to 3 hours or until firm enough to slice.
Heat oven to 350 degrees F. Cut logs in 1/4-inch slices. Place 1 inch apart on prepared baking sheets. Bake 8 to 10 minutes or just until edges and tops of cookies are firm. Transfer to wire rack; cool completely.
Spread the flat side of half the large cookies with 1 tablespoon Raspberry Filling (use 2 teaspoons filling for small cookies). Top with remaining cookies, flat sides to filling. Makes 22 large/30 small sandwiches.
In small saucepan melt white chocolate over medium-low heat; cool. Meanwhile, in large mixing bowl beat butter until creamy. Beat in raspberry preserves and vanilla. Gradually beat in powdered sugar and cooled white chocolate. Add whipping cream until spreadable.