1ouncedried porcini mushrooms , re-hydrated and chopped
2tablespoonsolive oil , plus more for grilling tomatoes
1/2teaspoonfreshly ground pepper
1 1/4poundsground beef(80/20)
1/2cupfontina cheese, cut into 1/4-inch cubes or coarsely grated
4ouncesprosciutto , cut into 1/4-inch pieces
3wholeCampari or Roma tomatoes, sliced thick
Place porcini mushrooms in a fine mesh strainer and rinse with cold water to remove dirt or debris. In a small bowl, soak mushrooms in 1 cup of red wine to re-hydrate, about 30 minutes (the wine should be room temperature or warmed slightly, not cold).
Once the mushrooms are hydrated and plump, drain over a measuring cup or bowl to reserve the liquid. Set liquid aside to allow any sediment to settle at the bottom of the bowl. Coarsely chop into 1/4-1/2 inch pieces.
Add 2 tablespoons of olive oil and garlic to a medium skillet and cook over med-low heat until garlic is fragrant. Add mushrooms to the skillet and cook for 1-2 minutes longer. With a small ladle or large spoon, add enough of the reserved mushroom liquid to the pan to loosen any browned bits; be careful to only use the liquid from the top and not to disturb the sediment in the bottom of the bowl.
Set mushrooms aside until ready to mix into the beef. Mix the pepper, onion powder, garlic powder, thyme, and oregano in a small bowl. In a large bowl, loosen the block of ground beef with your fingers and loosely spread it out in the bottom of the bowl. Sprinkle the beef with the seasoning mix.
Add the cheese, prosciutto, and mushrooms to the bowl and gently mix everything into the ground beef. Be sure to not over work the beef during mixing. Shape into patties with a small indention in the center of each patty using your thumb--this will keep the burger from curling or puffing.
Salt and pepper the sliced tomatoes and drizzle with olive oil. Grill along side the burgers until just softened.
Grill burgers over high heat until seared well on both sides and cooked through, roughly 4-5 minutes on each side. If there is room on the grill, toast buttered buns (butter side down) until toasted, while burgers finish. Otherwise, toast once burgers are done.
Garnish burgers with grilled tomatoes and fresh basil leaves.