You bake a special chocolate slice of my grandmother's famous (but secret) recipe. I can reveal that step 1 is to melt 250g of butter and add 1.5cups of brown sugar. After allowing the butter and sugar mixture to cool, you add 10mL of vanilla extract to an egg and mix. After adding the egg, you notice that the two-phase sugar-butter mixture becomes smooth and the sugar seems to have dissolved in the butter. The sugar dissolves in butter because the egg acts as an emulsifying agent. From a chemical perspective, how does the egg allow the butter and sugar to mix