Combine Baby Spinach, Milk, Dijon Mustard, Green Onions, and Garlic Clove in a saucepan. Cook on medium heat for 3-5 minutes or until heated through, stirring frequently. Cool slightly.
Pour contents of saucepan into a food processor or blender; cover. Blend until smooth.
Cook Burgers to order (4-5 minutes per side on high heat will usually yield Medium Rare).
In a medium pan, melt butter and scramble eggs.
Build your Burger: English Muffin Bottom, Burger, Eggs, Florentine Sauce, Crumbled Feta, English Muffin Top.