Step 1: Prepare Your Baking Vessels:

1. Preheat oven and prepare ramekins: Preheat your oven to 425°F (220°C). Grease and flour four 6-ounce ramekins. For gluten-free baking, it’s often recommended to use gluten-free flour for dusting, or you can use cocoa powder or even powdered sugar to prevent sticking. Alternatively, you can line the ramekins with parchment paper circles for easy removal.

Step 2: Melt the Chocolate and Butter:

1. Combine chocolate and butter: In a heatproof bowl set over a saucepan of simmering water (double boiler), combine the chopped bittersweet chocolate and cubed butter. Make sure the bottom of the bowl doesn’t touch the water.
2. Melt gently: Stir frequently until the chocolate and butter are completely melted and smooth. Remove the bowl from the heat.
3. Cool slightly: Let the chocolate mixture cool slightly for about 5-10 minutes. It should still be warm but not hot to the touch.

Step 3: Whisk Eggs and Sugar:

1. Whisk eggs, yolks, and sugar: In a separate large bowl, whisk together the whole eggs, egg yolks, and granulated sugar until pale and slightly thickened. This will help incorporate air and create a lighter texture.

Step 4: Combine Wet and Dry Ingredients:

1. Gradually add chocolate mixture to egg mixture: Slowly pour the slightly cooled melted chocolate mixture into the egg mixture while whisking constantly to combine. Ensure everything is well incorporated and smooth.
2. Whisk in dry ingredients: In a separate small bowl, whisk together the gluten-free flour blend and salt (and optional espresso powder). Gradually add the dry ingredients to the wet chocolate mixture, whisking until just combined. Be careful not to overmix, as this can make the cakes tough. If using vanilla extract, stir it in now.

Step 5: Fill Ramekins and Bake:

1. Divide batter: Divide the batter evenly among the prepared ramekins. Each ramekin should be about ¾ full.
2. Bake: Bake in the preheated oven for 12-15 minutes, or until the edges are set and the center is still slightly soft and molten. The baking time can vary slightly depending on your oven and the size of your ramekins. Start checking for doneness at 12 minutes. You want the edges to be firm but the very center to still look a little underbaked.
3. Cool slightly: Let the lava cakes cool in the ramekins for just a minute or two. This allows them to set slightly but keeps the center molten.

Step 6: Invert and Serve (Optional):

1. Invert onto plates (optional): If desired, carefully invert the lava cakes onto serving plates. To do this, run a thin knife around the edge of each cake to loosen it from the ramekin. Place a plate over the ramekin and quickly flip it over. Gently tap the ramekin to release the cake.
2. Dust with powdered sugar (optional): Dust the tops of the lava cakes with powdered sugar for a beautiful presentation.
3. Serve immediately: Gluten-Free Chocolate Lava Cakes are best served warm and immediately, while the center is still molten and gooey. Serve them plain or with your favorite accompaniments (see serving suggestions below).