To make the crust, put the flour, powdered sugar, and salt in a food processor and pulse to combine.
Add the butter and pulse until the mixture resembles cornmeal with some pea-sized chunks.
Whisk the egg yolk, and add it a little at a time, pulsing after each addition.
Turn the dough out onto a lightly floured work surface and gently knead until any extra flour is incorporated.
Press the dough into an 11-inch greased tart pan with a removable bottom. Freeze the crust for at least 30 minutes.
Preheat the oven to 375 degrees.
Top with a piece of non-stick foil or buttered foil and press it onto the surface.
Place the tart pan on a baking sheet and bake for 25 minutes or until the crust is golden brown.
Remove to a wire rack to cool completely.
When the crust is cooled, make the filling by placing all the filling ingredients in a bowl and beat until the mixture is smooth.
Scrape into the tart shell and smooth the top with an offset spatula.
To decorate, select the biggest blueberries and cut strawberries in half, removing the stems and hulls.
Whip cream with powdered sugar and pipe some rows of cream across the surface, leaving enough space between the cream for rows of strawberries.
Add strawberry halves, cut side down, in rows, then fill the open area with rows of blueberries.
Keep chilled until you serve.