Melt the butter in a small pan until bubbling. Add the onion and garlic and fry gently for 5 minutes until golden brown and soft.
Add the liver and cook for 2 minutes before adding the sherry, parsley, thyme salt & pepper stir for 1-2 minutes to burn off the alcohol and reduce the sherry. Remove from heat, then leave for 10 minutes to cool.
Place everything in a food processor and blend for a few minutes until the pâté is smooth.
Using a fine sieve, pass the pate through the sieve with a spatula to weed out any solids. Keep only the stuff that makes it through the sieve. This can be a messy business - sorry about that!
In a separate bowl, whisk the cream until you have stiff peaks.
Gently fold the cream into the pâté until it's all mixed through. Tip the pâté into a ramekin or bowl and cover with plastic wrap, pressed into the surface to stop any skin forming. Refrigerate until you need.
I like it served at room temperature, so remove from the fridge about an hour before you're serving.
For the onion jam
Heat the oil in a large frying pan over a moderate heat until hot then add the onion, garlic and oregano. Fry the onions for 4-5 minutes until softened then add the sherry. Let this sizzle briefly then add the chicken stock, salt and sugar. Let this come to a simmer then reduce the heat to low so that the onions are very gently simmering.
Cook for 1 hour uncovered, stirring regularly. If the liquid is absorbed, add a little amount of water at a time to keep things creamy.
After 1 hour, if there is any liquid, turn up the heat and cook til it's gone. Remove from the heat and cool completely.
Serving
Serve the pâté on toasted crusty bread with lots of onion jam over and good sprinkling of fresh parsley.