Preheat oven to 375°F.
In a small bowl, stir together flour, baking soda and baking powder. Set aside.
In a large bowl, cream together butter and sugar until smooth. Beat in the egg and vanilla. Gradually blend in dry ingredients. Add enough of the heavy cream to moisten the dough and make it soft but not wet.
Roll a cookie scoop (we used #30) of dough into balls and place on a parchment-lined cookie sheet. Slightly flatten the top of each cookie.
Bake for 8 to 10 minutes or until slightly golden. Let stand for 2 minutes before removing to cool on a rack.
For the frosting, in a standing mixer fitted with a whisk, mix together sugar and butter. Mix on low speed until well blended then increase speed to medium and beat for another 3 minutes.
Add vanilla and cream, and continue to beat on medium speed for 1 minute more, adding more cream if needed for spreading consistency.
Spread frosting on cooled cookies (Abby tip: To make the icing smooth put an offset spatula in warm water, wipe dry with a clean kitchen towel and smooth icing.). Decorate with candies.