Use a large sauce pan on medium heat and melt the butter. Add the garlic and onion and cook for 3 or 4 minutes to soften. Add the salt if using and the lemon juice.
Sprinkle in the flour and mix well with the butter and cook for a minute to eliminate the flour taste. Then whisk in the wine, lobster stock, cream, and brandy. Bring to a boil while stirring, then reduce to a gentle boil to reduce.
Reduce the sauce to the consistency of heavy cream which will take about 10 minutes. Stir in the hot sauce, taste and adjust the heat. Keep the sauce hot to serve or cool and reheat in a small skillet before serving.
Use a good non-stick skillet on high heat, add the canola oil. Lightly salt the scallops then add to the hot skillet and don't disturb for 2 to 3 minutes to sear the first side of the scallop. Use tongs to twist and lift the scallop and turn to the reverse side. Sear for another 2 minutes and watch for the scallop to turn opaque. Remove from the skillet.
Ladle a layer of the lobster brandy sauce on a plate and top with the seared scallops. Add a drop or two of truffle oil to each scallop.