Preheat oven to 350F (175C). Grease and flour a 9x13 inch baking pan.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large bowl, cream together the butter and sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla extract.
In a small bowl, whisk together the buttermilk and melted white chocolate.
Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk mixture, beginning and ending with the dry ingredients. Mix until just combined.
Gently fold in the crushed freeze-dried strawberries.
Pour the batter into the prepared pan and spread evenly.
Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes before inverting it onto a wire rack to cool completely.
Optional: Dust with powdered sugar or top with a white chocolate glaze.
Tips & Substitutions: For a more intense strawberry flavor, increase the amount of freeze-dried strawberries to 1 1/2 cups. If buttermilk is unavailable, a mixture of 1 cup milk with 1 tablespoon of lemon juice or white vinegar, allowed to sit for 5 minutes, can be used as a substitute.