Whisk together strawberry gelatin and boiling water in a large bowl until dissolved. Let sit until cooled to room temperature, about 5 minutes. Whisk in ¼ cup of the cream until fully incorporated. Refrigerate until starting to thicken, about 30 minutes.

Combine powdered sugar, vanilla (if using), and remaining 3 ¼ cups cream in the bowl of stand mixer. Beat, starting on medium-low speed and gradually increasing speed to high, until stiff peaks form, about 4 minutes total. Transfer to a large bowl, cover, and refrigerate until ready to use. Do not wipe mixer bowl clean.

Line an 8-inch square baking pan with parchment paper, leaving 2 inches overhanging on all sides. Place enough cookies in bottom of pan to form an even layer, breaking cookies as needed to fit. Set aside.

Combine cream cheese and sour cream in empty stand mixer bowl. Beat on medium-high speed until very smooth, about 2 minutes. Add 2 cups of the whipped cream and fold gently to incorporate. Spread half (about 1 ½ cups) of the cream cheese mixture on cookie layer.

Once strawberry layer has chilled, fold in 2 cups of the whipped cream and fresh strawberries until no streaks remain. Spoon half (about 2 cups) of the strawberry mixture on top of cream mixture.

Repeat layering with remaining cookies, cream cheese mixture, and strawberry mixture. Top with remaining 2 cups whipped cream, spreading in an even layer.

Refrigerate until set, at least 4 hours and up to 3 days. Top with more sliced strawberries and some crushed butter cookies.