Sift flours, baking soda, and salt into large bowl. Set aside.
In bowl of electric mixer or with a hand mixer, cream butter and sugar until fluffy, about 4 minutes. Add egg and vanilla, mix on low to combine. Continuing on low speed, gradually add flour mixture to mixer bowl, alternating with sour cream, until combined. Pack dough together, wrap in plastic; chill until firm, 2 hours or overnight.
Heat oven to 350°C. Tape a piece of parchment paper on the counter and dust the top of it with flour. Take a large chunk of dough, place it in the middle, cover with a large piece of plastic wrap and roll until 1/8 to 1/4 inch. Use cookie cutters to make your shapes, BUT DO NOT PULL AWAY SCRAPS. Move the piece of parchment to your baking sheet with cookies on it, without tearing away the scraps and put in freezer for five minutes.
Remove from freezer and tear away the scraps, then place evenly on the other baking sheet lined with parchment. Bake until just golden but not too brown, about 7 – 8 minutes. Transfer cookies to rack and let fully cool. Continue with dough; re-roll scraps and repeat the process with each batch.
Melt white chocolate chips and coconut oil on medium power, stopping to stir every 30 seconds. Decorate cookies with the glaze and whatever embellishments you’d like.