Preheat the oven to 350°F. Place the finely crushed pretzels in a mixing bowl.
Add 0.25 cup granulated sugar and the melted unsalted butter to the pretzels; stir until the crumbs are evenly moistened.
Press the mixture firmly and evenly into the bottom of an ungreased 9x13-inch baking dish. Bake until set and fragrant, 8–10 minutes. Cool completely on a rack, about 30 minutes.
In a large bowl, beat the softened cream cheese with 0.5 cup granulated sugar and the vanilla extract until very smooth, 2–3 minutes, scraping the bowl.
In a separate chilled bowl, whip the cold heavy cream to stiff peaks, 2–4 minutes. Fold the whipped cream into the cream cheese mixture until no streaks remain.
Spread the cream layer evenly over the cooled crust, pushing it all the way to the edges to seal. Refrigerate until firm, 20–30 minutes.
Meanwhile, pour the strawberry flavored gelatin dessert mix into a large bowl. Add the boiling water and whisk for 2 minutes until completely dissolved.
Stir in the cold water, then refrigerate the gelatin mixture, stirring every 10 minutes, until it is cool and slightly thickened with a syrupy consistency, 30–45 minutes.
Stir the hulled and sliced strawberries into the thickened gelatin.
Gently spoon the strawberry-gelatin mixture over the chilled cream layer, spreading evenly without disturbing the layer beneath.
Refrigerate uncovered until the gelatin is fully set, 2–4 hours (the center should jiggle slightly but not flow).