Spray 13 x 9 x 2 inch baking pan with nonstick cooking spray.
Blend flour, sugar and salt in food processor.
Add butter and vanilla; process until well blended and dough starts to form clumps.
Press evenly into prepared baking pan.
Bake at 325 for 10 minutes.
Remove from oven and while still hot, pierce dough all over with a fork. Using a sharp knife, cut dough into 12 squares, cutting through dough completely, then cut each square in half on the diagonal, forming 24 triangles.
Return to oven and continue baking for another 30-35 minutes until shortbread is golden brown, firm to the touch and crisp around the edges.
Remove from oven.
Using a sharp knife, immediately recut shortbread along same lines.
Cool shortbread in pan on cooling rack.
Place white chocolate in small bowl and microwave just until chocolate it melted and smooth. Using a fork, drizzle melted white chocolate in zigzag pattern over shortbread. Sprinkle evenly with almonds. Let stand until chocolate sets, about 1 hour.
Alternate chocolate drizzle:
Melt milk chocolate, butter and corn syrup in microwave just until chocolate is melted. Stir until smooth. Using the same technique, use a fork and drizzle melted chocolate in zigzag pattern over the shortbread and sprinkle evenly with almonds.