Preheat the oven to 425°F (220°C) and grease four ramekins with butter.

In a medium bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.

In another bowl, combine the egg, buttermilk, vegetable oil, vanilla extract, and red food coloring. Mix well.

Pour the wet ingredients into the dry ingredients and stir until just combined.

For the lava filling, heat the heavy cream in a small saucepan until it just begins to simmer. Remove from heat and add the chopped dark chocolate, stirring until smooth.

Divide the cake batter evenly among the prepared ramekins, filling them halfway. Add a spoonful of the chocolate filling into the center of each ramekin, then top with more cake batter until full.

Bake in the preheated oven for 12-14 minutes until the edges are set but the centers are still soft.

Let cool for 1 minute, then carefully invert onto plates and serve immediately with vanilla ice cream.