Editing Base Curry House Sauce (section)

==Instructions==
# Place the onions in a 3-litre (3 US quart) stockpot over medium heat and add the salt and oil.  Give it a good stir and then add the remaining vegetable and just enough water to cover.
# Bring to a simmer and then reduce the heat to low and simmer gently, covered for about 45 minutes.  
# After 45 minutes, your vegetables will be much softer and the liquid will have reduced some. Add the remaining ingredients and top up with water so that the water level is again about the same as before.
# Continue simmering for another 30 minutes. When the oil rises to the top and your veggies good and soft, youâre ready to blend.
# Using a hand-held blender, blend for about 3 minutes until the sauce is super smooth, with no chunks and not at all grainy. At this stage, the blended sauce might be quite thick. Add water until the sauce is about the same consistency as full fat milk or single cream. Sometimes I need to pour the sauce into a larger bowl to do this.
# Use immediately or store in the fridge for up to 3 days or freeze in small portions of between 500ml (2 cups) or 750ml (3 cups) for use later. The sauce can be frozen for up to three months.