Do you want a galaxy, ready to be served?
Here is the recipe you need:
Take at least 100 billion stars and interstellar gas you desire. Add interstellar dust and dark matter, as required. Cook the mixture at a temperature of 1032K and do not forget the fundamental ingredient: gravity!
Leave it all to cool for at least a billion years... and ready! you have a galaxy that you can serve! It seems easy to create a new galaxy, but really we did not know what a galaxy was, until a very few time ago. In the past, we didn't have powerful observation instruments as today, so galaxies seemed small regions, placed everywhere in the skies and featured by a bright vagueness, called, exactly, nebulas.
...and their origin
The wait is over: the engines of the LHC...
When two galaxies start to approach, the tidal attraction forces deform their structures...
All the existing galaxies, and our Milky Way too...