Remove any seeds from the mandarin quarters. Pulse mandarins in a food processor until just shredded but not mushy. Transfer to a heavy-bottomed saucepan, add 3 cups of water, and bring to a boil. Meanwhile, add Mulling Spices to the Muslin Bag and tie shut. Drop spice bag into the fruit mixture. Reduce to a simmer and cook for 30 min. or until the mandarin rind is soft. Remove spice bag and stir in lemon juice and sugar. Cook over low heat, stirring constantly, until sugar dissolves. Bring mixture to a rolling boil and cook at a boil for 30 min. to 1 hour until the setting point is reached.
Tip: To gague setting point, visually what you're looking for is the entire mixture to go from a fast boil with lots of frothing to a slow, sluggish plopping of the bubbles with no froth. This is when you know the mixture is thickening. To test the setting point, transfer a spoonful of marmalade to a bowl and letting it cool 1 min. Scoop it up with a wooden spoon. If the marmalade falls off the spoon in flake rather than a stream, then it is set.
Once setting point is reached, remove saucepan from heat and stir in spirit of choice. Ladle marmalade into sterilized canning jars, leaving ¼-inch headspace (the unfilled space between the marmalade and the jar’s lid) and gently seal with a two-part canning lid with band. Using tongs, lower jars into a pot of boiling water. Make sure the jars don’t touch and that the water covers the jars. Leave the jars in the boiling water for 5 min, then remove and let cool. You should hear a popping sound as each jar cools and seals. Let cool for 24 hours. Make sure each jar sealed by pressing your finger on the top of the lid; you shouldn’t feel any movement. Refrigerate any jars that did not seal properly. Enjoy within 9 months and refrigerate after opening.
Tip: If you want to skip the heat processing, simply ladle the marmalade into any sterilized jar with a tight-fitting lid, let it cool, and then refrigerate it. The refrigerated marmalade should be used within one to two months.