Put the mince, cream, egg yolks, 1 tsp salt and the pepper into a food processor. Blitz until smooth then place in the fridge and leave to chill for an hour.
Pour the breadcrumbs into a bowl with a pinch of salt. Form the mixture into four patties and dip into the breadcrumbs, coating them all over.
Preheat the oven to 170 C, Fan 150 C, Gas 3.
Put a knob of butter into a frying pan over a medium heat. Once the butter begins to sizzle add the patties and cook for 4-5 minutes on each side, or until golden brown. Place on a baking tray and put into the oven for a further 5-10 minutes until cooked through.
In the meantime bring a saucepan of salted water to the boil. Add the peas and cook for 5 minutes then drain. Add the stock and a knob of butter and blitz until smooth. Check seasoning and add salt if needed.
Spread a generous amount of pea puree onto each bun, then top with a lettuce leaf, a burger and a good smear of lingonberry jam.