Mistletoe and the Billionaire Boss

All I want for Christmas is a grumpy Santa in my stocking...
Despite having the misfortune to be called Mistletoe, I love everything about the festive season - from dressing the tree to baking the cake to wrapping the presents, even though I can't afford half the things I know my ten-year-old son, Finn, wishes for.
When the primary school where I work asks me to find someone to play Santa at the Christmas fair, I'm happy to oblige. Suddenly, though, every person I know is conveniently busy. The only guy available has the least amount of festive spirit of anyone I've ever met.
Alex Winters is the grumpiest man alive, but he is helping Finn to walk again, so I'm willing to overlook his grouchy temperament. It has nothing to do with the fact that he's the most gorgeous guy ever to wear a Santa suit. Unfortunately, though, he seems to find my sunshine personality more irritating than attractive, which is why, when he asks me to sit on his knee and tell him what I want for Christmas, I refuse to comply. But then he calls me a brat and threatens to put me over his knee, and suddenly I'm getting festive tingles in all the right places.
Finn hero-worships him, so as a special treat for my wheelchair-bound boy, and a secret present for myself, I invite Alex in for a drink after the office Christmas party. He turns out to have a heart of gold, frankincense, and myrrh that makes me melt. And his revelation of what he really thinks about me is a gift I never expected to get.
The twelve days of Christmas turn out to be a magical mystery tour that leaves me longing for more. But Alex is hiding a secret that's going to turn my world upside down...
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Contains no cheating, no cliffhangers, just a scorching romance and a heart-melting HEA: -)
Tropes include: Grumpy/Sunshine, one-night stand, fling, soul mates, instalove, alpha hero, billionaire