Instructions: In a 2- to 3-quart pan over medium heat, stir 1/2 cup butter and the brown sugar frequently until butter is melted and mixture is smooth, about 3 minutes.

Meanwhile, in a large bowl, mix oats, flour, baking powder, and salt. Add butter mixture; stir until well blended.

Add egg and vanilla to oat mixture and stir until well blended.

Drop dough in 1-teaspoon portions about 2 inches apart onto cooking parchmentulined or buttered and floured 12- by 15-inch baking sheets.

Bake cookies in a 350 degree regular or convection oven until browned, 8 to 10 minutes; if baking two sheets at once in one oven, switch their positions halfway through baking. Let cookies cool on sheets for 5 minutes, then use a wide spatula to transfer to racks to cool completely.

Spread the bottom of each of half the cookies with about 1 tablespoon Chocolate-Mint Ganache. Top each with a second cookie, bottom toward filling, and press gently to squeeze filling to edges of sandwich.

Chocolate-Mint Ganache: In a heatproof bowl set over (but not touching) barely simmering water in a pan, occasionally stir chocolate and whipping cream until chocolate is melted and mixture is smooth. Remove from heat and stir in peppermint extract. Let cool until thick but not firm, about 15 minutes, and use immediately.

This recipe yields about 3 dozen sandwiches.

Comments: Jane Shapton suggests sandwiching these thin, crisp oatmeal cookies around chocolate or peppermint frozen yogurt; we thought they were excellent filled with a chocolate-mint ganache. The filling is easiest to spread when slightly warm. If making it up to 3 days ahead, cover and chill, then stir gently in a bowl set over a pan of barely simmering water to rewarm. Fill cookies the day you serve them.

Yield: 3 dozen

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