Step 1: Prepare the Sugar Cookie Dough

1. Mix dry ingredients: In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
2. Cream butter and sugar: In a large mixing bowl, beat the softened butter and granulated sugar together with an electric mixer on medium speed until the mixture is light and fluffy. This will take about 3 minutes.
3. Add the egg and extracts: Beat in the egg, vanilla extract, and almond extract (if using). Continue mixing until everything is well incorporated.
4. Combine wet and dry ingredients: Gradually add the dry ingredients to the butter mixture. Mix on low speed until just combined. Be careful not to overmix the dough, as this can result in tough cookies.
5. Chill the dough: Divide the dough into two equal portions. Shape each portion into a disk and wrap it in plastic wrap. Chill in the refrigerator for at least one hour. Chilling the dough helps prevent the cookies from spreading too much during baking and makes it easier to roll out.

Step 2: Prepare the Stained Glass Center

1. Unwrap the candies: Unwrap the hard candies and separate them by color. Choose bright colors like red, green, yellow, and blue to create a festive stained glass effect.
2. Crush the candies: Place the candies in small plastic bags. Seal the bags and use a mallet or rolling pin to crush the candies into small pieces. You can also use a food processor, but be careful not to pulverize the candies into powder. The pieces should be small enough to melt smoothly but still large enough to maintain their shape when melted.

Step 3: Roll and Cut the Cookies

1. Preheat the oven: Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
2. Roll out the dough: On a lightly floured surface, roll out one of the discs of dough to about ¼-inch thickness. If the dough becomes too sticky, dust it lightly with flour as you roll.
3. Cut out shapes: Use festive cookie cutters to cut out shapes. You can use traditional Christmas symbols like trees, stars, and bells, or get creative with other shapes like hearts or snowflakes. Be sure to also cut out a smaller shape in the center of each cookie (for example, a circle or square) to create the “stained glass” window.
4. Transfer to baking sheet: Carefully transfer the cookies to your prepared baking sheets. Leave a little space between each cookie to allow for spreading during baking.

Step 4: Add the Stained Glass Candy

1. Fill the center with crushed candy: Spoon the crushed candy into the center of each cookie, filling the hole completely. Don’t worry if the candy overflows a bit; this will melt and spread as it bakes.
2. Bake the cookies: Bake the cookies in the preheated oven for 8-10 minutes, or until the edges are golden and the candy has melted into a smooth, glass-like consistency. Be sure to watch the cookies carefully so that the candy doesn’t burn.
3. Cool the cookies: Let the cookies cool on the baking sheets for 5-10 minutes, allowing the candy to harden. Once the cookies are cool enough to handle, transfer them to a cooling rack to cool completely.

Step 5: Decorate (Optional)

Once your cookies have cooled, you can decorate them with royal icing, edible glitter, or small candy pieces. Royal icing can be piped around the edges of the cookies or used to add intricate details. You can also sprinkle a bit of edible glitter on top to make them sparkle.