Erin Cusick’s workday begins at 3 p.m. in the office of Clover Club, the Brooklyn cocktail destination where she tends bar.

Long before a well-heeled crowd arrives to sip Coconut Juleps and rye Manhattans on Clover Club’s leather banquettes and barstools, Cusick is filling containers with dried limes and lavender sprigs, picking mint leaves (something she hates doing), slicing strawberries and oranges, and setting up a row of simple syrups and extracts in small bottles.

At 4 p.m., just as she finishes, the customers arrive — though she doesn’t love that term. “I hate calling them customers because when I bartend, it’s like you’re in my home, and I’m hosting a party for you,” Cusick says. “You’re my guest, you’re not my customer.”

Cusick starts her mornings like many New Yorkers, with a trip to a slightly overpriced gym ($80 a month, to be exact). There, she makes her health a priority by powerlifting. “In order to service others, you have to service yourself,” she says. “It makes me a better human for my guests.”

She eats breakfast in the form of a protein shake from the gym, making a point to tip the person who made it. Back at her $900-a-month apartment in Astoria, Cusick takes a shower. Her two roommates are reflections of what she is and could have been, she says. One is a bartender, like her, and the other is a “daywalker,” as she calls him, or someone with a 9-to-5 job.

After high school, Cusick studied English literature in college. Upon graduating, she worked as a dental assistant, a makeup artist for Chanel, a Barnes & Noble bookseller, and, for exactly three hours, a preschool teacher. She also worked at a “crappy family bar,” as she describes it, but dreamed of moving to NYC.

“I didn’t know I had a choice. In my town, you go to college after high school, get married and have babies,” she says. “If I had known, I would’ve moved to New York after high school. I would’ve been 10 years ahead of the game.”

At the start of the night’s service at Clover Club, guests plop down on the oversized bar stools. Sometimes Cusick strikes up a conversation with them and offers recommendations, sometimes they want to keep their heads down and have a drink. Whatever the circumstances, Cusick welcomes them with a smile before making them one of the 49 cocktails on the menu, almost all of which she has memorized.

Her coordinated hands begin the work, and she shifts her weight from foot to foot as she moves the length of the bar. She picks up ice, pours in booze and syrup, and muddles herbs or berries, all at lightning speed. Then, she caps the concoction in a shaker and shakes it authoritatively, all while discussing her love life or industry gossip with other employees at the pass.

When the cocktail is ready, Cusick pours it into a chilled glass, garnishes with bright leaves and presents it to the customer — err, guest — almost always eliciting an “Oooohh.”

Cusack first learned to do this dance at a bar in Astoria called the High Water. “That bar changed everything for me. It showed me that [bartending] isn’t just a job; it’s a career,” she says.

Now, bartending is her career. Cusick loves writing her own cocktail recipes and experimenting with different ingredients. Ultimately, she hopes to head up a bar and write menus.

“I do want to be in charge and run a team and programs and make things. Recipes, cocktails, menus, experiences — things people remember and go back to,” she says.

It’s not an easy career path, though. Cusick’s income fluctuates constantly. Her base pay, around $10 an hour, can jump to $20 or $30 depending on tips and traffic. She works five days a week, splitting her time between two bars, Clover Club and Pouring Ribbons. Like many service industry professionals, she has no health insurance or paid leave.

“If something happens to my hands, I’m out of work. Like, do I insure my hands?” she says, half joking. “I’d totally do that.”

Despite the risk and uncertainty, Cusick loves what she does. Why? She describes a recent moment at Clover Club, when two people sat at the bar.

“They looked super familiar, and we were making those faces like, ‘Do I know you?’” she recalls. Turns out, Cusick did kind of know them. She was their bartender at the High Water on their first date. And now, as their bartender at a different spot, Cusick was celebrating another special moment — their engagement.

“I started crying. That’s why I do what I do,” she says. “You’re a part of these moments and experiences, and you don’t even realize it.”