In a stand mixer or with a handheld mixer, cream the butter and sugar until light and fluffy.
Add eggs and vanilla, beating until the mixture is smooth.
Mix in flour, salt, and baking soda until just combined.
Pat chopped apples dry with a paper towel, then gently fold them into the dough. Cover and refrigerate for 1 hour to firm up.
For the streusel, combine butter, brown sugar, granulated sugar, cinnamon, flour, and oats, mixing until crumbly. Set aside.
Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.
Roll dough into 1-inch balls and dip the top half in streusel, pressing gently to stick. Place on baking sheets, spacing 2 inches apart.
Bake for 8-9 minutes, until edges are golden. Cool, then drizzle with a glaze of powdered sugar and maple syrup. Let set before serving.