Food trucks have long served as a proving ground for would-be restaurateurs, but over the past several years, the phenomenon of pop-up dining events have become equally celebrated for creating low-risk opportunities to test more daring and diverse foods. Across the state, you can now find everything from virtual hot pot dinners and Rhode Island-style weiners to a super collaborative Cambodian supper club attracting the best star talent. But the centerpiece of so many of these roving concepts is the burger.