Fast-food chain that began as a hot dog cart, and what this puzzle's circled letters do?

Now, in Nicaragua5 Shish __5 Org. for Sarah Strong and Hannah Hidalgo4 Slow to open up3 Feature of some happy and sad emoji4 Like a gooseberry4 Manilow's "hottest spot north of Havana," familiarly4 "I'll pay this time"4