Melt 2 tbsp butter in a small pot over medium-low heat, and add the shallot and garlic. Sweat them slowly for 2 or 3 minutes until they're soft but not browned. Add the apple juice and cider vinegar, and let simmer until only about 2 tbsp liquid remains.

Whisk 4 tbsp cold butter into the pot, one tbsp at a time. The sauce should thicken slightly as it emulsifies. Season with a pinch of salt and freshly cracked black pepper.

Turn the heat down to low and whisk in the heavy cream. Allow the sauce to warm up for 1 or 2 minutes, careful not to let it boil. For better presentation, strain the sauce through a fine mesh sieve. If you don't mind it rustic or simply run out of time (as I obviously did, from the picture), you can skip this step. Add the fresh herbs, adjust the seasoning, then turn the heat down to minimum as you cook the salmon.

Add a knob of butter and small splash of olive oil to a large pan on medium-high heat. Season the salmon fillets with salt and pepper, and fry them for 4 to 6 minutes per side, depending on thickness. Remove the fillets to a plate and carefully peel off the skins. Serve the salmon with a generous drizzle of the sauce.