Prepare Homemade Mustard: In a small bowl, combine brown and yellow mustard seeds, grinding them until fine. Mix with apple cider vinegar, water, a pinch of salt, and honey, then pour into a jar and let sit at room temperature for about 8 hours.

Slice the Croissants: Carefully slice large, flaky croissants in half and lay the bottom halves on a clean surface for easy assembly.

Assemble the Sandwiches: Spread a layer of jammy fig butter, layer with black forest smoked ham, Grand Cru cheese, micro greens, and spread whole grain mustard on top halves.

Finish with Seasoning: Preheat your oven to 375°F (190°C), brush honey on top halves, and sprinkle everything bagel seasoning on top.

Toast the Sandwiches: Bake in the preheated oven for 8-10 minutes, or until the cheese is melty and croissants are warm and flaky.

Serve and Enjoy: Remove from oven and allow to cool slightly before serving warm, preferably with a salad or potato chips.