Kat's Three Citrus Marmalade with Smoked Salt

I've got lots of friends who love to cook, but a few of them are truly exceptional. They take it to the next level...like my friend Kathryn. She could easily open up her own restaurant if she wanted to quit her day job. She has a culinary instinct that is unmatched and her annual six-course dinner has become legendary at my husband's place of work.  
You can imagine, then, how delighted I was when Kat sent me a little mason jar filled with Three Citrus Marmalade with Smoked Salt. It was absolutely delicious. I put it on a wonderful french bread I picked up at Colson's Patisserie. She paired it with a buttermilk scone.  Either way, you can't go wrong. Toast and marmalade make for a perfect breakfast or tea-time treat. This is also a great way to use seasonal winter citrus before local spring and summer fruits start coming onto the scene. 
Kat kindly let me post her recipe here, which is an adaptation of a Eugenie Bone recipe. I hope you enjoy it as much as I did...
Kat In Her Own Words:  
"Last weekend's little project was a collision of two marmalade recipes: Eugenia Bone's Three Citrus Marmalade, but with a smoked salt twist inspired by Anarchy In a Jar's Grapefruit Marmalade with Smoked Salt.
The resulting marmalade is a lovely, bright spread with the sweetness of Meyer lemons, the tartness of grapefruit and a slight bitterness that's balanced by a mild smoke flavor. Neither too bitter nor too sweet, I've been eating this every chance I can get! And I'm pretty sure I'm going to have to make another batch sometime very, very soon. Even though citrus isn't local, it certainly is seasonal, and I want to make sure that I'll have enough of this perfect marmalade to keep my pantry stocked all year long!"

Three Citrus Marmalade with Smoked Salt
adapted from Well-Preserved by Eugenia Bone

Yields a little more than 4 half-pints
2 grapefruits, pink or red
4 oranges (I used navel)
3 Meyer lemons
4 to 5 cups of sugar
1/2 t. unsalted butter
1/2 t. smoked sea salt

Peel the skin off of one orange and two lemons with a vegetable peeler and use the back of a knife to scrape off as much as you can of the white pith. Cut the cleaned rinds into thin matchsticks, then put them into a saucepan with 3 cups of water and cook over medium heat until tender. (About 20 to 25 minutes.)

Meanwhile, peel the remaining fruits. Cut them in half through the middle to remove seeds, then coarsely chop the oranges and lemons. For the grapefruit, cut supremes by slicing the flesh from between the membranes with a sharp paring knife. Measure the resulting fruit pulp and juice mixture - I had about four cups altogether. You'll want to match the amount of sugar to the amount of pulp; so for four cups of fruit, use four cups of sugar. If your yield is closer to five cups, use five cups of sugar.

Add the pulp, sugar, softened rinds and their cooking water to a large, heavy pot. (I used my IKEA dutch oven.) Cook over medium low heat, stirring occasionally, until the mixture reaches 220 degrees on a candy thermometer. (The original recipe suggests that this will take about 30 minutes; I found that it was more like 45 minutes, and required the heat being turned up to medium during the last 15 minutes.)

When the marmalade reaches 220 degrees, remove it from the heat and add the smoked sea salt. Continue to stir for three or four minutes while marmalade cools to insure proper distribution of the peels and pulp.

This recipe yields a little bit more than four half-pints of marmalade. If you're heat processing your marmalade for shelf-stability, jars should be processed for ten minutes. Otherwise, refrigerate cooled marmalade and eat within a week.