In a large bowl, cream butter and brown sugar until light and fluffy. Add molasses, egg, and vanilla; mix until combined. In a separate bowl, whisk together flour, spices, baking soda, and salt. Gradually mix dry ingredients into the wet mixture until a dough forms. Divide dough in half, wrap in plastic wrap, and chill for at least 1 hour.

Preheat oven to 350°F (175°C). Roll out dough to ¼-inch thickness on a floured surface. Use templates to cut out walls, roof panels, and any extra features (chimneys, doors, trees). Transfer to parchment-lined baking sheets.

Bake each batch for 15–20 minutes, or until edges are firm and slightly darkened. Let cool completely on wire racks before assembling.

In a large bowl, beat egg whites (or meringue powder mix) until foamy. Add cream of tartar and powdered sugar gradually, beating until stiff peaks form. Keep icing covered with a damp cloth when not in use to prevent drying.