This ham and Gruyère puff pastry slab looks highly technical. It requires almost no actual effort. The sweet maple-mustard spread anchors the savory filling while the sesame seed topping provides a distinct, shattering crispness on the first bite.
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The Secret to Maximum Pastry Height
Most filled pastries struggle to rise. This one puffs dramatically. Trimming a tiny sliver of dough off the sealed edges exposes the layers, allowing them to fan out rather than stay trapped. I assemble this entire slab up to four hours before baking. Cold pastry always puffs better than warm pastry, and the chill time sets the butter layers while I clean the kitchen.
How to Make the Pastry Slab
Preheat and prep. Heat the oven to 400°F (200°C). Unfold one thawed puff pastry sheet directly onto a parchment-lined baking sheet. Whisk the Dijon mustard and maple syrup together, then spread it evenly over the dough. Leave a strict 1-inch bare border around all four edges.
Layer the ham and Gruyère. Shingle the sliced ham evenly over the mustard spread. Scatter the grated Gruyère cheese loosely over the top.
Seal the pastry sheets. Brush the 1-inch bare bottom border lightly with your prepared egg wash. Drape the second pastry sheet over the top and press down firmly around the entire perimeter.
Trim and vent the dough. Trim roughly ⅛-inch off all four edges. I use a sharp pizza cutter instead of a knife for this step. It creates a clean downward cut without dragging, which keeps the delicate pastry layers from smearing together and refusing to rise. Cut 4 to 5 diagonal slits across the top pastry to let steam escape.
Garnish and bake. Brush the entire top with the remaining egg wash. Sprinkle evenly with sesame seeds, fresh thyme leaves, and cracked black pepper. Bake for 25 to 30 minutes. The pastry is done when it is deeply puffed and solid golden brown.
Cool before cutting. Let the pastry slab cool on the baking sheet for at least 10 minutes. This wait time allows the melted cheese to set slightly so it stays inside the crust when you slice the slab into 12 squares.
Make-Ahead and Storage Guidance
- Assemble ahead: You can build the unbaked slab up to 4 hours in advance. Cover it tightly with plastic wrap and chill it in the refrigerator. Apply the egg wash and toppings right before baking.
- Storing leftovers: Keep leftover squares in an airtight container in the refrigerator for up to 3 days.
- Reheating: Warm the squares in a 350°F oven for 5 to 7 minutes to restore the crispy texture. Microwaving makes the pastry soft and gummy.
Quick FAQs
Do I need to thaw the puff pastry first?
Yes, the pastry must be completely thawed but still cold to the touch. Thawing it overnight in the refrigerator is the safest method to prevent the butter layers from melting before they hit the hot oven.
Can I use a different type of cheese?
Swiss, provolone, or sharp white cheddar all melt beautifully in this filling. Avoid high-moisture cheeses like fresh mozzarella, which can release too much water and make the bottom crust soggy.
I prefer serving these squares warm, right after that short ten-minute rest on the baking sheet. The Gruyère is still soft, and the pastry flakes shatter instantly when you bite into them, making it exactly the kind of robust savory bite that disappears fast.
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Maple-Dijon Ham & Gruyère Puff Pastry Slab
This bakery-style savory slab pie looks incredibly impressive but comes together with minimal effort. We upgraded the classic ham and cheese filling with a sweet-savory maple-mustard spread, balanced the ingredient ratios so the pastry actually rises, and finished the crust with a sesame-thyme crunch that makes every square irresistible.
- Total Time55 minutes
- Yield12 squares (serves 12) 1x
Ingredients
Pastry & Filling
- 1 (17.3-oz / 490g) package frozen puff pastry (2 sheets), thawed overnight in the refrigerator
- 3 tablespoons (45g) Dijon mustard
- 1 tablespoon (15ml) pure maple syrup
- 6 ounces (170g) Black Forest deli ham, thinly sliced
- 6 ounces (170g) Gruyère cheese, freshly grated (about 1½ cups)
Egg Wash & Topping
- 1 large egg
- 1 tablespoon (15ml) whole or 2% milk
- 1 tablespoon (9g) white or black sesame seeds
- 1 teaspoon fresh thyme leaves
- ½ teaspoon coarsely cracked black pepper
Instructions
- Preheat and prep: Heat your oven to 400°F (200°C). Line a large, rimmed baking sheet with a piece of parchment paper.
- Mix the spread and egg wash: In a small bowl, whisk together the Dijon mustard and maple syrup. In a separate small bowl, beat the egg and milk together to create the egg wash. Set both aside.
- Build the base: Unfold one sheet of puff pastry directly onto the parchment-lined baking sheet. Gently smooth out any major creases with your fingers. Spread the maple-mustard mixture evenly over the pastry, leaving a strict 1-inch bare border around all four edges.
- Layer the filling: Shingle the sliced ham evenly over the mustard spread. Scatter the grated Gruyère cheese loosely over the ham, keeping it within that 1-inch border.
- Seal the edges: Brush the bare 1-inch border of the bottom pastry lightly with the egg wash. Carefully drape the second puff pastry sheet over the top, lining up the edges. Press down firmly all the way around to seal the top and bottom sheets together.
- Trim and vent: Using a sharp knife or pizza cutter, trim roughly ⅛-inch off all four edges. (A clean, downward cut removes the pinched dough and exposes the pastry layers, which helps the slab rise beautifully). Cut 4 to 5 diagonal slits across the top pastry to allow steam to escape.
- Garnish and bake: Brush the entire top of the pastry evenly with the remaining egg wash. Sprinkle the surface with the sesame seeds, fresh thyme leaves, and cracked black pepper. Bake for 25 to 30 minutes, or until the pastry is puffed, crisp, and deep golden brown.
- Cool and slice: Let the pastry slab cool on the baking sheet for at least 10 minutes before slicing into 12 squares. Serve warm or at room temperature.
Notes
- Why it works: Trimming a tiny sliver of dough off the sealed edges is the secret to maximum height. A sharp, clean cut prevents the pastry layers from fusing together, allowing them to fan out and puff dramatically in the oven.
- Make-ahead tip: You can assemble the entire unbaked slab up to 4 hours in advance. Cover it tightly with plastic wrap and chill it in the refrigerator. Wait to apply the final egg wash and toppings until just before baking.
Nutrition (per serving — estimates)
Calories: 280 | Total Carbs: 20g (Fiber: 1g, Sugar: 2g) | Fat: 18g (Saturated: 6g) | Protein: 10g
Nutritional values are approximate, based on standard reference data (USDA FoodData Central). Actual values vary by brand and exact measurements. For precision, use a tracker like MyFitnessPal or Cronometer.
- Prep Time: 15 minutes
- Cooling Time: 10 minutes
- Cook Time: 30 minutes
- Category: Appetizer
- Method: Baked
- Cuisine: American
Nutrition
- Serving Size: 1 square
- Calories: 280
- Sugar: 2g
- Fat: 18g
- Saturated Fat: 6g
- Carbohydrates: 20g
- Fiber: 1g
- Protein: 10g
