If croissants are very fresh and puffy, slice each croissant horizontally almost through so it opens like a book. If they are day-old and firm, gently press down while slicing so they open but remain in one piece.

Flatten

Lightly butter the inside of each croissant with about 1/2 teaspoon of the unsalted butter. Close and press each croissant flat with the palm of your hand to compress the layers slightly — you want a flattie that’s thinner and easier to fill and crisp.

Filling / Toppings (Savory Example)

Assemble savory filling

Spread about 1/4 teaspoon Dijon mustard on the bottom half of each croissant. Layer 1–2 slices of ham (or prosciutto) and 1 slice of Gruyère on each. Add a small handful (about 1–2 tablespoons) of baby spinach on top of the cheese. Season the spinach lightly with a pinch of salt and a grind of black pepper.

Heat and press

Warm a nonstick skillet or griddle over medium heat and add the olive oil or 1/2 teaspoon melted butter. Place croissants seam-side down, then weighted with a spatula or a small heavy pan to press (or use a sandwich press). Cook for 2–3 minutes until the bottom is golden and the cheese begins to melt. Flip carefully and press again for another 1–2 minutes until cheese is fully melted and the croissant is crisp on both sides.

Finish

Remove from heat and let rest 1 minute. Sprinkle each croissant flattie lightly with the remaining coarse salt and a tiny pinch of black pepper. Serve warm.

Optional Sweet Variation Toppings

Assemble sweet variation

For a sweet croissant flattie, spread about 1 tablespoon cream cheese on the bottom half and 1/2 tablespoon raspberry jam on the top half (or vice versa). Add sliced strawberries on the cream cheese layer.

Warm and caramelize (optional)

If you prefer the fillings warmed and slightly gooey, heat the skillet over medium-low with 1/2 teaspoon melted butter. Place the assembled sweet croissant seam-side down, press gently, and cook 1–2 minutes per side until golden and warmed through. Watch closely to avoid burning the fruit or jam.

Serve

Remove, let rest 30 seconds, then slice in half and serve warm or at room temperature.

Finishing

Final plating tips

Cut each croissant flattie in half on the diagonal and serve immediately. For savory, serve with a small green salad or pickles. For sweet, dust with a light shake of powdered sugar (optional) or drizzle a little extra jam. Leftovers can be reheated in a toaster oven at 350°F (175°C) for 5–7 minutes to re-crisp.