Boston Cream Roll Cake

1. Prepare the Sponge Cake:

1. **Preheat Oven**: Preheat your oven to 375°F (190°C). Grease and line a 15×10-inch jelly roll pan or baking sheet with parchment paper.

2. **Mix Dry Ingredients**: In a small bowl, whisk together the flour, baking powder, and salt.

3. **Beat Egg Yolks**: In a large bowl, beat the egg yolks with half of the granulated sugar (1/4 cup) until thick and pale. Mix in the milk, vegetable oil, and vanilla extract.

4. **Combine Dry Ingredients**: Gently fold the dry ingredients into the egg yolk mixture until just combined.

5. **Beat Egg Whites**: In a separate bowl, beat the egg whites until soft peaks form. Gradually add the remaining 1/4 cup granulated sugar, beating until stiff peaks form.

6. **Fold Egg Whites**: Gently fold the beaten egg whites into the cake batter until fully incorporated.

7. **Bake**: Pour the batter into the prepared pan and spread it evenly. Bake for 10-12 minutes, or until the cake is lightly golden and springs back when touched.

8. **Cool and Roll**: While still warm, turn the cake out onto a clean kitchen towel dusted with powdered sugar. Peel off the parchment paper. Roll the cake with the towel from one short side to the other, and let it cool completely.