For the sauce, heat the butter, add diced bacon and fry it until starting to brown.
Add the sliced button mushrooms and finely sliced shallots and soften in the butter.
Add the Madeira, flame off the alcohol and reduce to a syrup texture.
Add the chicken fond and reduce by two thirds.
Add the Debic Culinaire Original.
Reduce by one third of the volume.
Pass through a sieve, season the sauce with salt and balance the acidity with some lemon juice.