To make the onions: Coat a large saute pan with olive oil and add the onions. Season the onions with salt and bring the pan to a medium-high heat. Cover and sweat the onions for 15 to 20 minutes. Add the balsamic and cook for another 20 to 25 minutes or until the balsamic is syrupy. Use right away, or place in airtight jar and store in the refrigerator until ready to use.
To make the chicken liver pate: Coat a large saute pan with olive oil and add the anchovies, capers and garlic. Bring to medium heat and saute until the anchovies have dissolved.
Add the chicken livers, turn up the heat and saute for 3 to 5 minutes and cook until the livers are about 1/2 to 3/4 of the way done. Add the wine and cook for 3 to 4 minutes or until the wine has reduced by half, the mix should still be pretty soupy.
Transfer everything to a food processor and puree until smooth. Season with a little salt, if needed, and loosen with a little olive oil if needed.
Schmear each toast with the pate and top with balsamic onions.