Sift flours, baking soda, baking powder and salt into a bowl. Set aside.
Using a mixer fitted with paddle attachment, cream butter and sugars together until very light, about 5 minutes. Add eggs, one at a time, mixing well after each addition. Stir in the vanilla. Reduce speed to low, add dry ingredients and mix until just combined, 5 to 10 seconds (I like to cover the bowl with a towel, so you don’t have flour flying everywhere!). Drop chocolate pieces in and incorporate them without breaking them. Do the same with the blueberries.
Place dough in a gallon Ziploc bag and refrigerate for 24 to 36 hours. Dough may be used in batches, and can be refrigerated for up to 72 hours.
When ready to bake, preheat oven to 350 degrees. Line a baking sheet with parchment paper or a nonstick baking mat.
Scoop golf ball size mounds of dough onto the baking sheet. DO NOT roll dough into perfect balls. Simply dollop them onto the baking sheet, they look much prettier this way after they’ve been baked! Sprinkle with sea salt flakes and bake until golden brown but still soft, 12- 15 minutes (depending on your oven).
Transfer sheet to a wire rack for 10 minutes, then slip cookies onto another rack to cool a bit more.