Preheat the oven to 180°C, fan 160°C, gas mark 4.
Place the porcini in a small bowl and cover them in boiling water, leaving for 15 minutes.
When soft, add them and a few tablespoons of their soaking water with the butter to a pan.
Reduce at a rapid simmer until all the water has disappeared, then continue to cook the mushrooms until they turn a rich orange brown in colour.
Add the leeks and continue to cook the mixture for 10-12 minutes until very tender and the moisture has evaporated.
While the leeks cook, take a brioche bun and cut off the lid. Using your fingers hollow out most of the dough from the centre. The sides should be thin enough to get lots of filling in!
Stir the garlic into the leeks for a further minute or so, and add a generous grind of black pepper, squeeze of lemon juice and stir in the parsley.
Fill the brioche buns with this mixture, place the lid on top and place in the oven for 6-8 minutes until toasted.
Before serving, gently lift the lids and place a big spoonful of Philadelphia on top of the mushrooms, replacing the lid before serving.
Alternatively, use slices of a brioche loaf. Spoon the mushroom mixture over each slice of toasted brioche and top with a spoonful of Philadelphia to serve.
Cook's tip: Use Philly Light as a lighter option!
*All information included in this recipe has been provided by Mondelez UK.