Blackberry Jam Roly Poly

A roly poly, also known as a Swiss roll, is a flat sponge cake that's been covered in some sort of filling (in this case, blackberry jelly) and rolled up into a spiral to be sliced. I almost didn't post this because...well...I done messed it up bad. But it still tasted really good, so I decided I would post it anyway and just post a warning about how to NOT make the same mistake I did. The number one thing to be successful when making roly polys (polies?) is to use the thinnest parchment paper you can find. It turns out that the cheap, off-brand parchment paper I bought is thicker than most. Why does that matter? If your parchment paper is too thick, it won't be flexible enough to lay flat in the corners of your sheet pan. This will keep your batter from spreading far enough, which will make your sponge too thick, which will lead to breaking when you try to roll it (thinner sponges will flex more before breaking apart). So if you're smarter than I am, this should work out fine. If not, you'll end up with an ugly but tasty dessert.

 Blackberry Jam Roly Poly

Prep time: 10 minutes
Cook time: 10 minutes
Cool time: 10 minutes
Total time: 30 minutes

Yield: about 8 slices

Ingredients

• 1 1/2 cups flour
• 1 cup sugar
• 1 tsp baking soda
• 2 tsp baking powder
• 3 tbsp melted butter
• 1 tsp vanilla extract
• 1 tsp apple cider vinegar
• 1 cup milk
• Blackberry jelly or jam (about 1 cup, but just add as much as you want)

Directions

1. Preheat oven to 350F
2. Whisk together flour, sugar, baking soda, and baking powder
   
3. Whisk in melted butter (I forgot to take a picture here, but you'll end up with a clumpy-ish dry paste)
4. Whisk together vanilla, vinegar, and milk, then pour into dry ingredients and mix until smooth (batter will be thin)
   
5. Line a 9x13" baking sheet (one with a lip) with THIN parchment paper
6. Pour batter into sheet and spread evenly over the entire surface
   
7. Bake for about 10 minutes, or until golden brown. 
   
8. Let the sponge cool completely (about 10-15 minutes) on a cooling rack before removing from the baking sheet to invert it over another piece of parchment paper
   
9. Peel away the used parchment paper
   
10. Cut away any hard or overbaked edges to make an even rectangle
    
11. Cover the surface of the sponge with jam or jelly
    
12. Slowly roll the sponge into a spiral and slice into rounds (don't worry if this step turns into a disaster; it will still taste good!)