This is one of southern Italy signature preserve; pickled aubergine stored in olive oil. I have to say it was the first year I tried making them myself and I'm super happy how they turned out. 

It's hard to give proper proportions because it all depends on how many aubergines you'll want to start with. If you want at least 3-4 jars, you'll need at least 1kg of them. 

There's two main ways to make them and each family has it's own preferred one and adds its personal touches. It's up to you which one you'll pick, it will also depends on the time you have and want to spend making them. The faster way is the "cooked" pickled aubergines, the other is the "raw" pickled ones. In theory in both cases they're "cooked" by the vinegar so no worries. Below I've added both.

Ingredients for the "raw" pickled version 

• aubergines - better if they're the light purple variety but the most common dark ones also work 

• white wine vinegar 

• salt

• garlic

• (optional) herbs such as mint, basil and parsley 

• olive oil - in case you can use a mix of olive oil and sunflower seeds oil 

Ingredients for the "cooked" pickled version 

• aubergines - better if they're the light purple variety but the most common dark ones also work

• 1.5l of white wine vinegar - the water-vinegar ratio is 1:3

• 500ml of water

• salt

• garlic

• (optional) herbs such as mint, basil and parsley

• olive oil - in case you can use a mix of olive oil and sunflower seeds oil 

Preparation of the "raw" pickled version 

1. Slice the aubergines in thin short slices

2. in a bowl place the aubergines and layer them with vinegar and salt, ending with a layer or vinegar and salt 

3. cover the bowl with a plate and add a weight to serve as a press

4. let the aubergine "cook" in the vinegar for an entire day

5. drain the aubergines with the help of a colander

6. leave the aubergines in the colander in the sink or in a wider bowl, cover them with a plate and add a weight to serve as a press for 12 hours - or all night
   
7. with the help of a kitchen towel and wring out the leftover excess liquid from the aubergines - it's easier if you do it in small batches
   

8. season the aubergines with a little bit of oil, garlic and the herbs

9. fill each sterilised jar with the aubergines slightly pressing on them and add if you want a leaf of basil and slice of garlic clove

10. pour the oil into the jars until the aubergines are fully covered - it might take you a few times as the oil will set slowly filling the air bubbles therefore you might have to top it up

Preparation of the "raw" pickled version

1. Slice the aubergines in thin short slices
   
2. place the aubergines in a colander and layer them with salt ending with the layer of salt
3. cover the colander with a plate and add a weight at a press
4. let them drain their liquid for at least 2 hours - therefore, place the colander either in the sink or in a big bowl, but in that case make sure you empty it every once in a while 
5. rinse the aubergines
6. in a pot bring the water and vinegar to boil 
7. boil the aubergines for approximately 5 minutes
8. drain the aubergines and place them on a kitchen towel to dry 
9. season the aubergines with a little bit of oil, garlic and the herbs
10. fill each sterilised jar with the aubergines slightly pressing on them and add if you want a leaf of basil and slice of garlic clove
11. pour the oil into the jars until the aubergines are fully covered - it might take you a few times as the oil will set slowly filling the air bubbles therefore you might have to top it up
    

In this cake, since the aubergines have been pickled and vinegar, it's not necessary to sterilise the filled jars. At the same time, you need to make sure the jars have properly sealed, the lid does not have to make any clicking sound. If it's not the case, then sterilise the jars.