Whisk together half-and-half, eggs, and vanilla. Dip croissant halves into mixture. Cook pecans, honey, and 2 Tbsp. butter in a saucepan until hot. Keep warm. Melt 1 Tbsp. butter in a nonstick skillet or griddle over medium heat. Add 4 croissant halves; cook until golden brown. Repeat. Serve with honey mixture.