Step 1

Heat the oven to 375°F. Spread the walnuts on a baking sheet and bake for about 10 minutes or until toasted, stirring halfway through. Grind them in a food processor until they are in pieces about the size of mini chocolate chips. Remove all but 1/4 cup from the food processor, then grind the remaining 1/4 cup quite fine, like sprinkles.

Step 2

In a stand mixer or using a hand mixer, cream the butter and sugar until fluffy, then add the eggs and vanilla. Add the flour, baking soda, baking powder, and salt and beat briefly until just combined. Stir in the oats and 1 1/2 cups of the larger walnut pieces by hand. (At this point the dough can be used immediately or refrigerated for up to 3 days.)

Step 3

Over medium-low heat, warm the condensed milk and chocolate chips in a small saucepan until the chocolate chips are completely melted. Stir to combine and keep on very low heat.

Step 4

Lightly grease a cookie sheet and dollop out small rounds of the cookie dough by the spoonful. Flatten into nests with the back of the spoon or your fingers.

Step 5

Spread a teaspoonful of the chocolate mixture on top of each cookie dough nest. Cover the dough nest almost completely; the cookie will spread out around the chocolate. Sprinkle some of the remaining 1/4 cup of finely chopped nuts on top.

Step 6

Bake at 375°F until just lightly golden brown, 12 to 15 minutes. Let cool on the cookie sheet for a few minutes then remove to a cooling rack.

Step 7

Store in a covered container for up to 5 days (or however long you can make them last).