Bring cranberries, 1 1/3 cup sugar, 1/2 water, salt and orange peels to a boil over medium heat in a medium size saucepan. Lower heat to a simmer, cover. Simmer for 10 minutes or until cranberries have burst and mixture thickens.

Whisk 4 egg yolks and 2 tsp corn starch together in a small bowl. Remove the orange peel from the cranberries. Pour the cranberry mixture into the bowl of a food processor, add in the egg yolk mixture and process until smooth about 1 minute. Scrape down the sides. Leave mixture to cool in the food processor about 30 minutes. A skin will form- this is fine.

Add the softened 4 TBSP of butter to the cranberry puree and process another 30 seconds until smooth. Strain the mixture over a fine mesh sieve into a large bowl. It helps to use a scraper to press the puree through the sieve. Remove about 2 TBSP of the curd and place in a bowl with the 1 cup of heavy whipping cream and 2 TBSP of sugar. Chill the cream mixture.

Pour the strained curd into the prepared (baked) tart shell. Let tart rest at room temperature for 4 hours or cover loosely and place in a fridge until serving. Overnight is fine. The tart will set up nicely.

In the bowl of a stand mixture, whip the cream mixture on high until stiff peaks form. Place into a piping bag with a large pastry tip and pipe a decorative border on the tart. Serve immediately.