Make the cognac hot with the whipping cream, but do not boil on the stove top. Remove from the heat. Add the coconut oil and butter and dissolve.
Cut off the whole milk and semi-sweet couvertures and whisk in a small saucepan in a bain-marie over low heat until smooth, stirring with a whisk into the whipped cream and fat mixture. Pour the truffle mixture into a glass or possibly metal mold (20 x 150 mm) lined with plastic wrap, cover with foil and refrigerate for one night.
Turn out of the mold, remove the foil and cut into cubes. Quickly arrange cubes into a ball. Meanwhile, keep balls and quantity chilled.
For the icing, chop the milk cooking chocolate into pieces and stir in a small saucepan in a bain-marie over low heat until smooth. Dip the truffle balls into the cooking chocolate with a praline fork, let them drain and become firm. Roll in sifted cocoa or fine sugar.
Keep refrigerated in neatly sealable tins.
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Tip: Feel free to use better chocolate – the more delicious the result!