Salmon Belly Crudo with Fennel and Tangerine Gastrique

In a small saucepan set over medium-high heat combine the sugar and both vinegars. Bring to a boil. Lower the heat to medium and add the chopped fennel fronds and about half of the tangerine zest. Continue cooking until reduced to about 3/4 cup. Strain the syrup through a fine mesh sieve into a small bowl and allow to cool completely. Discard solids.Meanwhile, put the tangerine juice in a medium bowl.

Add the cooled tangerine and vinegar syrup a little at a time, completely incorporating each addition until you have a gastrique that is thick and viscous but not syrupy. You might not use all the tangerine and vinegar syrup. Stir in half of the remaining zest and a small pinch of salt. Taste the gastrique, adjusting seasoning as needed. If it needs a little more acidity, add as much or as little of the lemon juice as needed. It should be bright and tart with a hint of tangerine sweetness.Use a mandolin to slice the fennel and radish into very thin slices.Using a very sharp knife (and a single long slicing motion per section) cut the the salmon belly into ¼-inch slices. Trim the salmon removing any skin and cut it into bite-sized pieces.Arrange the salmon and radish slices in an alternating pattern across a chilled serving platter. Pile the fennel slices attractively to one side and then garnish with the tarragon leaves and the remaining tangerine zest. Finish with a little sea salt, and then drizzle some of the gastrique all around the plate.