Preheat oven to 350ºF. In a medium bowl, stir together graham cracker crumbs with sugar, then add melted butter and stir until thoroughly combined. Press the mixture into a 9" tart pan with removable bottom and bake 10 minutes. Cool completely on a wire rack.
Meanwhile, make the filling. Combine the white chocolate and 1/3 cup of the whipping cream in a medium microwave-safe bowl. Microwave on 50% power for one minute, stir, then microwave again in 30-second intervals until chocolate is about 75% melted; stir to melt the rest. Cool the chocolate mixture to room temperature on the counter (do not refrigerate or it will cool unevenly and harden at the edges).
Whip the remaining cream with electric mixer to stiff peaks. Fold 1/3 of the whipped cream into the cooled chocolate (by gently cutting it down through the centre with a spatula and scooping back up and over until fully incorporated). This lightens the mixture so you don't deflate the whipped cream. Gently fold in the remaining whipped cream.
Scrape the filling into the cooled crust and smooth the top. Refrigerate until set, 2-3 hours, then top with the strawberries. Melt the jam in a small saucepan or in the microwave, then brush on top. Serve immediately or return the tart to the refrigerator to set the jam, about 30 minutes.