Line heavy large baking sheets with parchment paper and set aside.
Preheat the oven to 325 degrees F.
Finely chop the oats in a food processor.
Mix in the flour, baking powder, baking soda, and salt.
Using an electric mixer, beat the butter and sugars in a large bowl until fluffy.
Scrape down sides of mixing bowl.
Beat in the eggs and almond extract.
Add the flour mixture in 3 parts and stir just until blended.
Stir in the chocolate chips and chopped almonds.
For each cookie, drop 1 rounded tablespoonful of dough onto the prepared baking sheets, spacing 1-inch apart (do not flatten dough).
Bake until the cookies are golden (cookies will flatten slightly), about 13 minutes.
Cool the cookies on the baking sheets for 5 minutes.
Transfer to a cooling rack and cool completely.
The cookies can be prepared 1 day ahead.
Store airtight at room temperature.
To make the ice cream sandwiches: Place the ice cream in a large bowl.
Mix in the amaretto.
Cover the ice cream mixture and freeze until firm, at least 3 hours.
Arrange 12 cookies, flat side up, on a baking sheet.
Top each with a scoop of ice cream, then another cookie, flat side down, pressing slightly to adhere.
Cover and freeze the sandwiches until they are firm, at least 3 hours.
Sandwiches can be made up to 4 days ahead.
Wrap each sandwich with plastic wrap and keep frozen.