Preheat the oven to 350°F, then lightly grease the bottom of a 9×13-inch baking dish with butter.

In a medium bowl, stir together the crushed pretzels, ¾ cup sugar, and melted butter until combined. Press the mixture firmly into the bottom of the prepared pan. (To crush the pretzels, place them in a Ziploc bag and use a rolling pin, wooden spoon, or your hands.)

Bake the pretzel crust for 10 minutes. Remove it from the oven and let it cool completely.

In a large mixing bowl, beat together the cream cheese, remaining ¾ cup sugar, and vanilla until smooth and fully combined. Gently fold in the Cool Whip.

Spread the cream cheese mixture evenly over the cooled pretzel crust, making sure it reaches all the way to the edges to create a seal that prevents the gelatin layer from soaking into the crust.

In a medium bowl, whisk the gelatin into two cups of boiling water until fully dissolved. Stir in the sliced strawberries, then refrigerate for about 15 minutes, just until the mixture begins to thicken but is not set.

Slowly pour the strawberry gelatin mixture over the cream cheese layer. Cover the dish and refrigerate for about 2 hours, or until the gelatin is fully set. Slice into squares before serving.