Make the porcini butter: Bring the water to a boil in a small saucepan. Remove from heat, stir in the mushrooms, and let stand 20 minutes.
Remove mushrooms, chop finely and set aside. Strain the mushroom liquid through a paper coffee filter and then return to the saucepan. Simmer until reduced to about 1 tablespoon. Cool.
Add cooled mushroom liquid, butter, garlic, and lemon zest to bowl with chopped mushrooms. Mix well with a fork. Season with salt and pepper.
Transfer butter to a sheet of wax paper and roll into a 6-inch log. Wrap well and twist ends closed. Wrap in foil. Refrigerate for up to 2 days or freeze for up to 1 month. Return butter to room temperature before serving.
Make the bundles: Blanch the beans in a large pot of boiling water until crisp-tender, about 5 minutes. Transfer immediately to a large bowl of ice water. Drain and pat dry.
Preheat the oven to 400 degrees. Place a strip of ham on a clean work surface. Arrange about 12 beans in a bundle at one end of the ham and roll up so that the ham forms a belt around the center.
Place the bundle in a large baking dish. Repeat with the remaining beans and ham to make a total of eight bundles.
Bake until the beans are warm and tender, 13 to 15 minutes.
Top each bundle with a pat of porcini butter and a sprinkling of crispy onions and parsley. Serve warm