The Essentiel Antwerp Hapricorn buttondown shirt updates a classic silhouette with square-sequin floral embellishments. The Essentiel Antwerp Hapricorn buttondown shirt updates a classic silhouette with square-sequin floral embellishments. After launching a successful T-shirt collection that quickly took over their apartment, husband-and-wife designers Esfan Eghtessadi and Inge Onsea opened their first boutique in Antwerp, Belgium in 2000. Today, Essentiel Antwerp is a complete ready-to-wear line marked by playful prints, pop colors, and spot-on detailing.