A sure sign of spring: our 91-square-foot “Mini Jeni’s” in German Village—the one with the dandy walk-up/bike-up window at 900 Mohawk St.—re-opens for the season on Saturday, April 1. (No joke!) Our ambassadors will be scooping from noon to 10 p.m. daily. Here’s the opening weekend menu: Ndali Estate Vanilla Supermoon Darkest Chocolate Salted Peanut…