Preheat and Prep Pans: Preheat the oven to 350°F. Coat 2 (8-inch) round cake pans with baking spray and line with parchment paper.
Make Cake Batter: Whisk dry ingredients (flour, gelatin, baking powder, salt, baking soda).
Beat butter and sugar until fluffy, then mix in eggs and vanilla.
Alternate adding dry ingredients and buttermilk.
Divide batter between pans.
Bake Cake: Bake for 40 minutes, then cool in pans for 10 minutes.
Transfer to wire racks to cool completely (1–1.5 hours).
Prepare Frosting: Beat butter and salt until creamy, then mix in vanilla.
Gradually add powdered sugar and cream, beating until smooth and fluffy.
Make Crumble: Pulse cookies, freeze-dried strawberries, and salt in a food processor. Drizzle in melted butter and pulse until combined but slightly chunky.
Assemble Cake: Trim cake tops if needed. Frost the first layer, add the second, and frost the entire cake.
Add Crumble: Press crumble over the top and sides of the cake. Chill for 1 hour before serving.