How to Make It
Preheat the oven to 375°F. Spread the whole almonds or almond slivers on a baking sheet pan. Roast for 6 minutes or until lightly toasted. After they have cooled enough to handle, roughly chop the almonds. Set aside.
In a bowl, whisk together the flour, baking powder, and salt. Stir in the oats. Set aside.
In a mixer, beat together the butter and brown sugar until well combined, about 1 minute. Beat in the eggs and vanilla. Stir in the flour mixture until just combined. Stir the chopped almonds into the batter. Chill the dough for at least 1 hour or up to overnight (the dough can also be pre-scooped and frozen for future use).
If the oven has been turned off, preheat the oven to 375°F. Line a couple sheet pans with parchment paper. Scoop the heaping tablespoon sized portions of the dough onto the lined sheet pans, spacing them about 1 1/2-inches apart. Lightly press the almond slices into the tops of the cookies.
Bake for 12-14 minutes or until the cookies are lightly browned. Let them cool for a few minutes and then transfer to a wire rack to finish cooling.