A perfect condiment to your favourite burger, caramelized onion relish gives this sweet tone and makes your burger onions easier to digest! Perfect with a beef and halloumi burger!
Clean and slice the onions. Melt the butter on medium-high heat and add the sliced onions. Sautée for about 10 minutes, stirring constantly to prevent the onion from frying; it should just sweat and get soft. Set the water to boil.
After 10 minutes, add the sugar and stir for a couple of minutes. Then pour in the Balsamico and stir until it has evaporated (another couple minutes). Pour in the boiling water, close the lid, lower the heat to medium and let simmer for 15 minutes, checking from time to time.
Remove the lid and simmer uncovered for a couple of minutes to evaporate any excess water that has not been absorbed by the onions. This is ready to serve.
Store any leftovers in an airtight container for up to a week. The butter will solidify in the fridge, so I recommend microwaving before the next use to get to the original texture.