1. Preheat the oven to 400 F (200 C) degrees.
2. Melt together the butter, brown sugar, and corn syrup in a small saucepan over low heat.
3. Stir in the nuts and the flour.
4. Line an unwarped baking sheet with parchment paper. Bake the cookies one baking sheet at a time, four cookies to the sheet, allowing 1 rounded tablespoon of batter per cookie. Put 4 spoonfuls on the baking sheet, spaced equally apart, and flatten them slightly with damp fingers.
5. Bake for about 7 minutes. For even baking, rotate the baking sheet midway through baking. When done they will be a deep, golden brown.
6. Remove from the oven and cool briefly, about 1 minute. Using a metal spatula, lift each cookie off the baking sheet and drape over overturned teacups to form the cookie cups. If they cool too quickly, before you have time to shape them, they can be softened by putting them back in the oven for 1 minute.
7. Allow the pan to cool, then continue baking additional cups.
8. Store the cooled cups in an airtight container until ready to serve. These are best eaten within a few hours of baking.