Preheat oven to 350°. Place 2 (12-cavity) silicone molds† on a rimmed baking sheet.
In a large bowl, stir together granulated sugar, brown sugar, and oil. Add egg, egg yolk, and vanilla, stirring to combine.
In a medium bowl, sift together flour, cocoa powder, baking powder, baking soda, and salt. Gradually add flour mixture to sugar mixture alternately with milk, beginning and ending with flour mixture, stirring just until combined after each addition. Using a 2-teaspoon levered scoop, portion 2 scoops of batter into each cavity.
Bake cakes until a wooden pick inserted in centers comes out clean, 10 to 12 minutes. Let cool in moulds for 10 minutes. Freeze for 20 minutes before removing from moulds.
Place Earl Grey Buttercream in a piping bag fitted with a rose tip (Wilton #102). Pipe frosting in a zigzag design on tops of cakes. Sprinkle with chocolate pearls, if desired.
Notes
Make-Ahead Tip: Store decorated cakes in a single layer in airtight containers in the refrigerator for up to 2 days. Let come to room temperature before serving.
*We used Valrhona Dark Chocolate Crunchy Pearls. †We used Celebrate It 12-Cavity Nugget Silicone Treat Molds from Michaels.
Recipe by TeaTime Magazine at https://teatimemagazine.com/london-fog-tea-cakes/