Name: Creamy Cremini Turnovers
Yield: Makes 10 turnovers
Ingredients: 1 large egg; 1 Tbsp water; ½ cup plus 1 Tbsp [130 g] water, ice cold; Water, for brushing; 1 Tbsp olive oil; 1⅔ cups [230 g] diced yellow onions (½ in [12 mm] pieces); 1 Tbsp unsalted butter; 2 Tbsp chopped fresh dill; ⅓ cup plus 1 Tbsp [95 g] sour cream; 1⅔ cups [230 g] all-purpose flour, plus more for dusting; 1 tsp fine sea salt; 1 cup [220 g] unsalted butter, cold, cut into ¼ in [6 mm] cubes; 1½ tsp fine sea salt, plus more for seasoning; 1 tsp freshly ground black pepper; 1 cup [100 g] thinly sliced leeks; 7½ cups [450 g] sliced cremini mushrooms or mini portobello mushrooms (¼ in [6 mm] slices); 1 egg yolk

Whether your New Year’s Eve fête involves a large gathering or a party of one on the couch, little appetizers like our mushroom turnovers are bound to make it feel special. And bonus: Assembled, unbaked turnovers freeze well, so you can be ready for a celebratory shindig anytime. (Want to make this recipe simpler? Buy pre-made puff pastry. It’s okay. We won’t tell.)