As for cookies, I spent about two years tweaking my used-to-be-perfect-at-sea-level-cookie recipe so you don't have to go through the hundreds and batches and delicious calories that I did (hey, someone had to do it. You're welcome).
(I usually double the recipe, but I'm not the boss of you)
1 cup butter, softened
3/4 cup white granulated sugar
3/4 cup brown sugar
3/4 tsp. baking soda
2 large eggs
1 tablespoon vanilla extract (I prefer vanilla bean paste if you can find it)
2 3/4 cups white flour
1 1/2 cups mix-ins (chocolate chips, dried fruit, nuts, etc)
Preheat oven to 350 degrees F. Cream butter and sugars. Add eggs, one at a time, mixing after each. Add Soda, salt, and vanilla. Add flour and mix well. Add mix-ins. Drop by heaping teaspoon (or use cookie scoop) onto a baking sheet lined with parchment paper or a silpat mat. Bake at 350 for 9-11 minutes, until edges are barely brown. Remove from oven and let sit on cookie sheet for 3-5 minutes to cool and set.