I did not expect to find the best store-bought matzo ball soup I've ever tasted in a mall in Essex. May my Jewish grandmothers and mother forgive me, but Leo & Co.'s version even beats most homemade ones I've sipped. With every spoonful, the rich, savory broth served at the new café and market felt like it was infusing restorative roasted-chicken and vegetable goodness deep into my bones. The $6 serving boasted abundant diced carrots and celery and two plump matzo balls. Tender but with a springy bounce, those traditional dumplings are made from Manischewitz gluten-free matzo ball mix elevated by a not-so-secret home cook trick. "We add seltzer to the batter, just like every good Jew," said Leo & Co. proprietor Kayla Silver, who opened Salt & Bubbles Wine Bar and Market in summer 2021 in the same Essex Experience building as her latest venture. Going gluten-free makes the soup accessible to more people, Silver added. Surprisingly, the matzo balls don't suffer — and Leo & Co.'s 31-year-old New York City-raised owner knows from matzo balls. They are the only clue to Silver's heritage on the menu of creative sandwiches, baked goods, soups and salads, although she did name the business after a beloved great-uncle, Leo Keiles. Despite the tragedy he endured, including surviving the Holocaust and later losing his only child, "Leo was just brightness. He was like light in a room," Silver said. "The man never left anywhere without making a friend." Keiles and his wife ran a candy store in Dallas for many years, and he relished fine foods, Silver said. "He firmly believed if it wasn't good, if it wasn't tasty, don't eat it." Uncle Leo's spirit is well represented in his grand-niece's bright, friendly and decidedly tasty counter-service café and market. Leo & Co. opened in July in the large space vacated when Sweet Clover Market ended its 17-year run. With a comfy couch area and farmhouse-style tables set on area rugs, the café invites customers to settle in. On any given day, Leo & Co. might host colleagues discussing projects over excellent coffee (from $3), brewed from nearby Uncommon Coffee's freshly roasted beans; or eating breakfast sandwiches made with fluffy, cream-enriched local eggs on house-baked English muffins. The $7 meaty sandwich option comes with bacon and onion jam, but I preferred the $6 veggie for its punchy sun-dried tomato relish and…