2. Half fill the saucepan with salted water and bring to a boil. Put in the piece of fish, bring back to a boil, cover and simmer very gently for 20 minutes.

3. Turn off the heat and allow the fish to sit in the water while you make the sauce (do not let sit for more than 20 minutes or so).

4. Put egg yolks in a heavy stainless steel saucepan on low heat or in a bowl over hot water (double boiler). Add the water and whisk thoroughly.

5. Add the butter, bit by bit, whisking all the time. As soon as one piece melts, add the next. The mixture will gradually thicken, but if it shows signs of becoming too thick or slightly scrambling, remove from heat immediately and add a little cold water. Do not leave the pan or stop whisking until the sauce is made. If the sauce is too slow to thicken it may be because you are excessively cautious and the heat is too low. Increase the heat slightly and continue to whisk until the sauce thickens to a coating consistency.

6. Add lemon juice to taste.

7. Just before serving, skin the salmon and lay it on a hot serving dish. Garnish with parsley, fennel leaves and lemon wedges and serve with the Irish butter sauce.