Prepare the cookie dough: Cream together the unsalted butter and granulated sugar until fluffy and light. Beat in the large egg, vanilla extract, and strawberry powder until well combined. Gradually add in the all-purpose flour and salt to form a soft dough. Chill the dough in the refrigerator for 30 minutes.

Roll and shape the cookies: Preheat your oven to 350°F (175°C). Once chilled, roll out the dough to about ¼-inch thickness. Use a cookie cutter or knife to cut out boat shapes or ovals, carefully creating indentations in the center with your thumb or a spoon.

Bake: Line baking sheets with parchment paper and place your cookie shapes on top. Bake for 12-15 minutes until the cookies are set but not browned. Let them cool completely on a wire rack after baking.

Make the filling: In a mixing bowl, beat together the mascarpone cheese, heavy cream, powdered sugar, and vanilla extract until thick. Transfer the filling to a piping bag or a zip-top bag with a corner snipped off for easy piping.

Prepare the glaze: In a small saucepan, heat strawberry jam with a bit of water until it becomes smooth and pourable. Set it aside to cool slightly.

Assemble the boats: Once the cookies are cooled, pipe the creamy filling into each indent of the cookie boats. Arrange fresh sliced strawberries on top, and then brush the glaze over the strawberries for a beautiful shine. For added texture and visual appeal, sprinkle shortbread cookie crumbs on top.

Serve: Chill the assembled cookie boats in the refrigerator until ready to serve, but allow them to sit at room temperature for 15 minutes before enjoying to enhance the flavors.