Ham and Gruyere Thumbprints

Preheat oven to 400 degrees. Bring butter, salt, and the water to a boil in a large, heavy saucepan over medium heat, stirring occasionally (butter will melt). Add flour; stir vigorously until incorporated. Continue to cook, stirring, until the mixture pulls away from sides of pan and a thin film forms on bottom of pan, 1 to 2 minutes. Remove from heat; let cool 2 minutes.

Transfer dough to a large bowl; add eggs 1 at a time, beating with a wooden spoon to incorporate each before adding the next, about 2 minutes. Stir in pepper, ham, and shredded cheese.

Spoon dough into a pastry bag fitted with a 1/2-inch star tip. On a baking sheet lined with a Silpat baking mat or parchment paper, pipe 1 1/2 inches wide rosettes, 1 inch apart. Make a deep indentation at the center of each with your thumb (dampen thumb to keep it from sticking to dough). Bake until crisp and golden, 25 to 30 minutes.Transfer thumbprints to a wire rack to cool completely. Press a cheese cube into indentation of each.

Place on clean baking sheets; freeze (uncovered) until firm, about 1 hour. Transfer to an airtight container; freeze until ready to use, up to 6 weeks.

To serve, preheat oven to 425 degrees. Place thumbprints on ungreased baking sheets; bake until heated through and cheese is melted, 10 to 14 minutes. Serve warm.