Step 1: Make the Meringue (Pavlova Base)

1. Preheat your oven to 250°F (120°C). Line two baking sheets with parchment paper.
2. In a clean, dry bowl, whip the egg whites on medium speed for 1 minute.
3. Slowly add the sugar while whipping. Once all the sugar is added, increase the speed to high and whip for 10-12 minutes until stiff peaks form. The meringue should look glossy.
4. Gently fold in the cornstarch and lemon juice with a spatula.
5. (Optional) For a swirl effect, brush food coloring inside a piping bag before adding the meringue.
6. Pipe the meringue into small nest shapes (about 3½ inches wide), leaving space in the center for the filling.
7. Bake for 1 hour, then turn off the oven and let the pavlovas sit inside for another 30 minutes to prevent cracking.

Step 2: Make the Blackberry Jam

1. In a small saucepan, combine blackberries, sugar, lemon juice, and water.
2. Bring to a boil over medium heat, stirring occasionally, for 5-10 minutes.
3. In a small bowl, dissolve 1 tbsp cornstarch in 2 tbsp water and stir into the blackberry mixture.
4. Cook for 1 more minute, then let the jam cool completely in the fridge before using.

Step 3: Make the Whipped Cream

1. Right before assembling, whip cold heavy cream with powdered sugar and vanilla on medium-high speed for about 3 minutes, until soft peaks form.
2. Transfer to a piping bag for easy assembly.

Step 4: Assemble the Pavlovas

1. Spoon blackberry jam into the center of each pavlova.
2. Top with whipped cream and fresh blackberries.
3. Serve immediately for the best texture.