A Myer lemon panna cotta topped with an intensely lemon marmalade makes for a cool, light and flavorful dessert. Even better, you can make this one a day or two in advance.
Prepare the lemons as follows: Using a vegetable peeler, remove the peel in one long strip from three of the lemons. Start at one end and remove the peel in a circular fashion until you have one long spiral. Set aside. Zest the fourth lemon using a fine-gauge micro planer, so you have about 2 T of very fine zest. Juice all four of the lemons and divide into two half cup portions. Set aside.
Put half a cup of lemon juice in a small bowl. Sprinkle 1 packet of Knox plain gelatin on top and allow to soften for about 15 minutes.
Put cream and milk in a heavy-bottomed sauce pan. Slit the vanilla bean from end to end, scrape seeds into pan and drop in the bean. Add lemon zest and 1/2 cup sugar and heat until the mixture just comes to a boil, stirring to dissolve the sugar. Remove from heat, cover and let steep for 15 minutes.
Remove vanilla bean and briefly whisk milk and cream mixture to break up any vanilla seeds that may be clumped together. Whisk in lemon and gelatin mixture into the warm cream to dissolve. If your cream mixture has become too cold, you may need to briefly heat up the cream mixture to dissolve the gelatin, then remove from heat. Whisk in yogurt and divide into 6 ramekins or decorative glasses. Each portion will be about 3/4 cup. Allow to cool to room temperature, cover with saran wrap and refrigerate for at least 3 hours or over night.
Put the lemon peel strips in a small, heavy-bottomed sauce pan and cover with water. Bring to a boil and continue to boil for 5 minutes. Pour out water, cover with more water and boil for another 5 minutes. Repeat one more time and drain rind. This process helps remove any bitterness in the lemon rind. Slice rind strips into 1/4″ slices and set aside.
Put remaining 1/2 cup of lemon juice, 1/4 cup of water and remaining 3/4 cup of sugar in the pan and heat over medium, stirring to dissolve sugar. Add lemon rind slices and continue to cook on low heat for about 18 to 20 minutes, stirring, until the mixture has thickened and reduced to about 3/4 cup. Remove from heat and allow to cool. Transfer into a storage container, cover and refrigerate until ready to serve.
If you have used straight-sided ramekins for the panna cotta, unmold onto individual serving plates. You can slide a knife around the edges or dip in hot water for a few seconds to help the unmolding. Top each panna cotta with a big spoonful of lemon marmalade. If you have chilled the panna cotta in decorative serving glasses, simply top each glass with a spoonful of marmalade.