
If you’ve spent any time on TikTok in the past year, you’ve likely seen countless iterations of the viral upside-down tartlets. This beginner-friendly pastry hack transforms store-bought puff pastry and the sweet or savory filling of your choice into a beautiful bite-sized snack. We’ve seen videos using sliced apples, tomatoes, and even caramelized onions. Our version leans heavily into savory territory with a cream of mushroom soup-inspired filling.
You can find mushroom used two different ways here: both sliced and in a creamy, cheesy filling. The filling starts with a classic combination of minced mushrooms and shallots known as a duxelles (the very same mixture you can find at the base of a beef Wellington.) To make this filling more mushroom soup-esque, we supplement it with Gùyere, heavy cream, and either sour cream or crème fraîche. The tangy dairy offsets some of the richness of the pastry while still containing enough fat to avoid curdling in the oven.
When working with puff pastry, it’s important that you avoid prolonged exposure to heat. The dough is stacked with layers and layers of cold butter, which should melt and produce steam in the oven to create that signature flaky texture. Allowing that butter to melt while the dough sits on the counter will sacrifice that essential puff. If you notice your pastry start to warm up or stick to the counter, transfer it to a parchment-lined baking sheet, and let it cool down in the refrigerator for 10 to 15 minutes before you start working with it again.
The best part about this recipe is that you can make most of the components ahead of time. The mushroom filling can be made up to 3 days in advance, while the puff pastry squares can be cut and refrigerated up to a day before serving.
Did you make these tartlets? Let us know how it went in the comments!
Ingredients
- 8 oz.
baby bella mushrooms, divided
- 1
large shallot, coarsely chopped
- 1 Tbsp.
vegetable oil
Kosher salt
- 1 oz.
Gruyère cheese, grated
- 2 Tbsp.
heavy cream
- 2 Tbsp.
sour cream or crème fraîche
- 1/2 tsp.
cornstarch
- 1/2 tsp.
fresh thyme leaves, chopped
All-purpose flour, for surface
- 1
sheet frozen puff pastry, thawed
Directions
- Step 1Preheat oven to 375° and line 2 baking sheets with parchment. Slice 4 oz mushrooms into 1/4" slices; set aside.
- Step 2In a food processor, pulse shallot and remaining 4 oz. mushrooms until finely chopped, about 15 times.
- Step 3In a medium skillet over medium-low heat, heat oil. Add shallot mixture; season with salt. Cook, stirring occasionally, until light brown and most of the liquid is evaporated, about 15 minutes. Transfer mushroom mixture to a medium bowl and cool slightly.
- Step 4Add Gruyère, heavy cream, sour cream, cornstarch, and thyme and mix until thoroughly combined.
- Step 5On a lightly floured surface, lay pastry flat. Cut into 12 (3") squares. Place 2 slices reserved mushrooms directly on parchment on a prepared sheet. Top with 1 tbsp. filling. Arrange a pastry square on top of filling and gently press around the edges to enclose. Repeat with remaining tartlets, spacing about 2" apart (you should have 6 on each sheet).
- Step 6Bake tartlets until pastry is puffed and golden brown, 15 to 20 minutes. Let cool slightly, then invert onto a wire rack and let cool completely.
- Step 7Make Ahead: Filling can be made 3 days ahead.. Store in an airtight container and refrigerate. Puff pastry squares can be cut to size1 day ahead. Place on a parchment-lined sheet, tightly wrap with plastic wrap, and refrigerate.

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