Fig Jam: Place figs in a large saucepan over high heat. Add sugar, lemon juice, water and salt and bring to a boil. Stir until sugar dissolves. Reduce heat to a simmer and continue to cook, uncovered until the fruit is soft and the mixture has thickened, about 45 minutes.
Remove from heat. Spoon the jam into jars. Seal and let come to room temperature.
Store in refrigerator for up to 3 months.
Marsala Mushrooms:
Heat 1 Tbsp. butter in a large saute pan over medium high heat. Add mushrooms and cook, stirring often until you see the mushrooms begin to release their moisture.
Add the garlic , thyme, salt and pepper and continue to cook until most of the water evaporates.
Add the remaining 1 Tbsp. butter and continue to cook for 3-4 minutes until mushrooms are nicely browned.
Add the Marsala wine and increase the heat to high and bring to a boil. Continue to boil until the Marsala has cooked down. Remove from heat.
To assemble the sandwiches:
Spread 1 1/2 tsp. Dijon mustard on 2 slices of the toasted artisan bread.
Top the Dijon mustard with some arugula, then 3 slices prosciutto, some sliced Asiago cheese and some Marsala mushrooms.
Spread 2 tsp. fig jam on two more slices of toasted bread and place on top of sandwich.
Secure the sandwich with a bamboo skewer threaded with 2 sweet gherkins.