Alright, a true Hollandaise sauce this is not, by a long shot, but I wanted something similar to Eggs Florentine/Eggs Benedict, and here's what I did: I layered sauteed spinach, smoked Norwegian salmon, and two fried eggs in a bowl, and then I made this pan sauce which did a perfect job tying it all together. Sorry that the measurements are approximate. Adjust to taste. I didn't season it because I seasoned my spinach well and the salmon itself is quite salty. Give this a try, it's delicious!
1 knob (about 2 Tbsp) mascarpone cheese
1/2 Tbsp butter
3/4 tsp mustard (stone-ground, dijon, or horseradish--not yellow)
juice of 1/2 a small lemon
1) Combine all over very gentle heat, stirring constantly, until melted and combined. Use immediately.