Prepare the base dough: In a stand mixer fitted with the paddle attachment, cream butter, sugar, and salt on medium speed until light and fluffy (about 3-4 minutes). Scrape down the sides of the bowl frequently.
Add the egg yolks and vanilla and mix until fully incorporated, about 1 minute. The mixture should look smooth and creamy.
Gradually add the flour with the mixer on low speed, about ½ cup at a time, mixing just until combined. Be careful not to overmix or your cookies will become tough.
Divide the dough into portions depending on how many variations you plan to make. For 6 variations, divide into 6 equal portions (about 1 cup each).
Customize each portion by gently folding in the mix-ins for your chosen variations. For spiced variations, knead the spices in gently; for add-ins like chocolate chips or nuts, fold them in carefully.
Wrap each portion separately in plastic wrap, flattening into discs, and refrigerate for at least 1 hour or up to 3 days.
Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.
Shape your cookies according to the variation:- For cut-out cookies: Roll dough to ¼-inch thickness and use cookie cutters- For thumbprints: Roll 1-inch balls, make an indentation with your thumb- For slice-and-bake: Form dough into logs, chill thoroughly, slice into ¼-inch rounds- For snowballs: Form into 1-inch balls Arrange cookies on baking sheets with about 1½ inches between each cookie. They won’t spread much but need room for even baking.
Bake in batches for 10-12 minutes, rotating the pan halfway through, until the edges are just barely golden. The centers should still look slightly soft.
Cool completely on the baking sheet for 5 minutes, then transfer to wire racks.
Apply finishes once cookies are fully cooled:- For chocolate-dipped: Melt chocolate with coconut oil, dip half of each cookie- For jam thumbprints: Fill indentations with preserves before baking- For glazed cookies: Mix powdered sugar with lemon juice, drizzle over cookies- For snowballs: Roll in powdered sugar while still warm, then again when cool Allow all decorations to set completely before packaging, at least 2 hours or overnight for chocolate-dipped varieties.
Assemble your gift boxes by lining with parchment paper and carefully arranging different cookie varieties. Layer with additional parchment if stacking.