1. Preheat oven to 350°F (175°C) and grease an egg-shaped silicone mold or mini muffin tin.

2. In a large bowl, whisk together melted butter and granulated sugar, then mix in eggs one at a time, and stir in vanilla.

3. In a separate bowl, sift together the flour, cocoa powder, and salt.

4. Gradually add the dry ingredients to the wet ingredients, mixing just until combined, then fold in optional chocolate chips.

5. Spoon batter into the prepared mold, filling each cavity about two-thirds full, and bake for 15-20 minutes.

6. Let the brownies cool in the mold for 10-15 minutes before transferring them to a wire rack to cool completely.

7. Make the icing by whisking together powdered sugar, a tablespoon of milk, and vanilla extract, adding more milk until a smooth, drizzlable consistency is reached.

8. Divide the icing into separate bowls, add food coloring to each, and drizzle over the completely cooled brownie bites.