Prepare the Sponge Cake:

1. Preheat the Oven:
   • Preheat your oven to 350°F (175°C). Grease a 10×15-inch jelly roll pan, line it with parchment paper, and grease the parchment.
2. Beat the Egg Yolks:
   • In a large bowl, beat the egg yolks and 1/4 cup of granulated sugar until thick, pale, and doubled in volume (about 3 minutes). Add the vanilla extract and mix.
3. Beat the Egg Whites:
   • In a separate clean bowl, whisk the egg whites and salt until soft peaks form. Gradually add the remaining 1/4 cup of sugar, beating until stiff peaks form.
4. Combine the Mixtures:
   • Gently fold the egg whites into the yolk mixture in three additions, being careful not to deflate the batter.
5. Add Dry Ingredients:
   • Sift the flour and cornstarch together over the egg mixture and gently fold until just combined.
6. Bake the Cake:
   • Spread the batter evenly into the prepared pan. Bake for 10-12 minutes, or until the top springs back when lightly touched.
7. Roll the Cake:
   • Dust a clean kitchen towel with powdered sugar. While the cake is still warm, turn it out onto the towel, peel off the parchment paper, and roll the cake gently from the short side with the towel. Let it cool completely in the rolled shape.

Prepare the Filling:

8. Whip the Cream:
   • In a chilled bowl, beat the heavy cream, powdered sugar, and vanilla extract until stiff peaks form.

Assemble the Cake Roll:

9. Unroll the Cake:
   • Carefully unroll the cooled cake. Spread a thin, even layer of raspberry jam over the cake, followed by the whipped cream, leaving a 1/2-inch border around the edges.
10. Roll the Cake:
    • Gently re-roll the cake without the towel, being careful not to squeeze out the filling. Place seam-side down on a serving platter.

Garnish and Serve:

11. Decorate:
    • Dust with powdered sugar and garnish with fresh raspberries, mint leaves, or festive decorations. Refrigerate for 1 hour before slicing and serving.