Preheat oven to 350 degrees. Line two mini-muffin pans with foil or paper liners (Note: you might not use all 48 liners).
Heat butter and molasses in a small saucepan on medium heat until butter melts and molasses just boils. Pour into the mixing bowl of a stand mixer and let cool for 5 minutes.
Sift together dry ingredients (flour, baking soda, milk powder if using, ground spices, and salt), and use a fork or whisk to combine.
After butter/molasses mixture has cooled, add sour cream, lemon curd, and orange zest and mix on low to combine.
Keep mixer on low speed and gradually add dry ingredients to wet ingredients; mix until just combined.
Using a small scoop, put batter into lined muffin pans; fill about 2/3 full. Bake 12-13 minutes until a tester or toothpick comes out clean. Remove from oven and let cool in pan for about 10 minutes before removing from pan and placing on a cooling rack.
Let gingerbread cupcakes cool completely before frosting. Option 1: Leave gingerbread cupcakes without frosting. Option 2: Dust with confectioner's/powdered sugar if you don't want to make frosting.
Frosting: Combine cream cheese, butter, lemon curd (if using), and vanilla extract in mixing bowl and mix until combined and smooth. With mixer on low speed, gradually add confectioner's/powdered sugar until it's smooth and the desired consistency. If it seems thin, add more sugar. If it seems stiff, add a few drops of milk to thin.
Frost gingerbread cupcakes after they are completely cooled.
This recipe makes 12 full-size cupcakes (bake for 25-30 minutes) or two 8"x8" cakes (bake for 35 minutes, rotating pans halfway through). A toothpick should have only fine, dry crumbs; if it comes out wet, bake for another few minutes.