The Franklin Inn houses a bustling Mexican cantina

The Franklin Inn is in a tiny, nondescript building on Rochester Road in a residential part of the North Hills. If you don't know what you're looking for, it's easy to pass it by.

From the outside, the Franklin Inn looks like a friendly neighborhood bar. That's right, in part. But the secret that Franklin Inn's regular customers don't want to advertise is that it also is a favorite Mexican restaurant where long waits on the weekends are the norm.

Customers vie for 50 close-set seats nearly every night, owner John Cibula says. "On weekends, we turn over the tables four times," he adds. "Some of our customers walk here."

In business since the 1930s, The Franklin Inn has been owned by the Cibula family since 1978. Henry and Sue Cibula, John's parents, originally served American food until 1983, when his mother decided to try Mexican food on the slow days, which were Tuesdays and Sundays.

Those days quickly became the restaurant's busiest, Cibula says, so the family changed the menu and restaurant into a Mexican cantina, long before chains such as Chi-Chi's became popular.

"Mexican saved the day," says Cibula, who has owned the restaurant for two and a half years. "My parents used to run a house down there in Mexico and brought back recipes."

They also brought back lots of colorful Mexican decorations that hang on the dark walls of the 50-seat restaurant. Cibula says that dinner time is so busy, especially in the summer, that people have to wait outside for a table to open.

When the place really gets hopping, head chef and kitchen manager Karen Matulevic and six full- and part-time line cooks have to try hard not to bump into each other in the cramped kitchen.

Cibula is Slovakian, and none of his staff is Mexican. Yet they know how to make a mean burrito or a scrumptious quesadilla; sauces are made fresh daily. Tortilla chips are fried in peanut oil on the premises.

Cubula says the restaurant's hot wings are popular, and the potato pepper soup is a big seller. (His mother adapted the soup from a Mexican recipe.) "We go through a ton of it," Cibula says. "I don't know anybody else who has one like this."

The soup incorporates potatoes with the skins on and fresh poblano peppers. It's easy to make and is great served with crackers, burritos or some kind of bread.

However, have a box of tissues nearby to dab at your watering eyes.

Poblano peppers — long, tapering chiles with thick flesh, a medium-to-hot flavor and a dark green color tinged with purple or black — are available at Hispanic markets and at many grocery stores. Sometimes they are labeled (imprecisely) as pasilla . Use rubber gloves when handling them for this recipe to prevent burns, and avoid contact with your eyes.

When buying chicken base, make sure that "chicken" is first on the ingredients list to ensure the best flavor.

• 1 tablespoon chicken base
• 1/2 gallon chicken broth
• 1 1/4 cups Spanish onions, cut in 1/4-inch dice
• 2 cloves garlic, peeled and finely chopped
• 1 cup poblano peppers, diced
• 1 1/4 cups ripe tomatoes, cut in 1/4-inch dice
• 1 1/4 pounds potatoes, skins on, cut in 1/4-inch dice
• 1/2 bunch fresh cilantro, diced
• 1 tablespoon salt, or to taste
• About 1 cup Monterey Jack and Colby cheeses, shredded
• Fresh cilantro sprigs (for garnish)

Assemble ingredients for the soup.

Add the chicken base to the chicken broth and heat. Add the onions, garlic, poblano peppers, tomatoes and potatoes. Simmer for 1 hour.

About 10 minutes before the soup is cooked, add the diced cilantro and salt. Serve garnished with the cheeses and sprigs of fresh cilantro.