Preheat oven to 450 degrees F. Slice croissants horizontally to form two sandwich halves. Line up sandwiches on a work surface for easy assembly. On each bottom half, layer two slices of ham and a slice of manchego cheese. Add a generous spoonful (about 1.5-2 tablespoons) of bacon jam and spread evenly. Top bacon jam with a small handful of spinach leaves. Top sandwiches with the other half of the croissants and arrange on a baking sheet.
Bake sandwiches in preheated oven for about 10 minutes, until spinach is wilted, croissant is toasted, and cheese is melted.
Recipe by Wright Family Table at https://www.wrightfamilytable.com/toasted-croissant-sandwiches/