Prepare the Strawberry Filling: Combine sliced strawberries, sugar, cornstarch, and lemon juice in a medium saucepan. Cook over medium heat, stirring frequently, until the mixture thickens and the strawberries soften (about 8-10 minutes). Remove from heat and let cool completely.

Make the Crunchy Cookie Topping: Place Oreo cookies in a food processor and pulse until they form coarse crumbs. Mix with melted butter and sugar until well combined. Set aside for later.

Bake the Vanilla Cake: Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans. In a large bowl, cream together butter and sugar until light and fluffy. Add eggs one at a time, then mix in vanilla. Gradually add flour mixture alternating with milk, beginning and ending with flour.

Assemble the Layers: Divide cake batter between the two prepared pans. Bake for 25-30 minutes or until a toothpick inserted comes out clean. Cool cakes completely before assembling. Place one cake layer on a serving plate, spread with cooled strawberry filling, then top with second cake layer.

Add the Final Touch: Sprinkle the crunchy cookie topping generously over the top of the cake. For a funfetti-style look, you can press some of the topping into the sides of the cake as well.