Preheat the oven to 350?F (175?C).

In a mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.

Add the eggs and vanilla extract, mixing until well combined.

In a separate bowl, whisk together the flour, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Chill the dough in the refrigerator for 15 minutes.

Roll out the chilled dough on a floured surface to about 1/4 inch thick.

Use a cookie cutter to cut out shapes and place them on a baking sheet lined with parchment paper.

Bake in the preheated oven for 10-12 minutes or until the edges are lightly golden.

Remove from the oven and let cool completely on a wire rack.

In a mixing bowl, beat the softened butter until creamy.

Gradually add the powdered sugar, mixing until smooth.

Add the heavy cream and vanilla extract, beating until fluffy.

Divide the frosting into separate bowls and add food coloring to each to create different colors.

Spread or pipe the cream frosting onto the cooled cookies.

Use additional decorations like sprinkles or edible glitter to enhance the unicorn theme.