Place the cherries, sugar, and rum in a saucepan. Cook for about 7 minutes, then let cool. Separate the cherries from the liquid, and return the liquid to the heat to reduce by half.

Prepare the cake. Beat the eggs with the sugar and salt until the mixture is light and fluffy. Sift the flour, baking soda, and cocoa together. Gradually add the flour mixture to the eggs, gently folding with a whisk without overmixing to avoid adding too much air.

Lay the cake out on plastic wrap or parchment paper. Brush with the cherry syrup and spread the filling evenly. Place the boozy cherries along one long edge of the cake. Using the edge of the plastic wrap, carefully roll up the cake. Without removing the wrap, chill the chocolate Yule log in the refrigerator for about 2 hours.

For the decoration, beat the egg yolks with the sugar and 1 teaspoon lemon juice until thick and creamy. Cover the log with a thick layer of the cream to resemble a heavy layer of snow on the log.