Cream the softened unsalted butter and granulated sugar until light and fluffy, about 3-5 minutes. Beat in the egg and vanilla extract, then mix in the strawberry powder.

Gradually add the all-purpose flour and salt, mixing until a dough forms. Chill the dough in the refrigerator for 30 minutes.

Preheat your oven to 350°F (175°C). Roll out the chilled dough and cut into boat shapes, creating indentations in the center of each cookie. Bake for 12-15 minutes until slightly golden.

In a mixing bowl, combine mascarpone cheese, heavy cream, and powdered sugar. Beat until the mixture holds stiff peaks, then add vanilla extract.

Once cookies are cooled, fill each with cream and top with fresh strawberries. Brush with thinned strawberry jam and sprinkle with cookie crumbs if desired.

Chill assembled cookie boats in the refrigerator for at least 30 minutes before serving. Allow to sit at room temperature for 10-15 minutes before enjoying.