Steps
1. Preheat your oven to 350°F (175°C) and grease a small ramekin or oven-safe dish.
2. In a mixing bowl, whisk together the flour, sugar, baking powder, and salt.
3. In another bowl, combine the milk, vanilla extract, melted butter, and egg yolk, mixing well.
4. Gradually add the wet ingredients to the dry ingredients, stirring until just combined.
5. Pour the batter into the prepared ramekin and smooth the top.
6. Bake in the preheated oven for about 20-25 minutes, or until a toothpick inserted in the center comes out clean.
7. Allow to cool slightly before enjoying your mini vanilla cake.