
Place the butter in a pot and heat over medium - high heat. Melt the butter while stirring.
Keep heating the butter to make brown butter. Make sure to keep stirring the butter during the process.
The butter will first melt and then come to a boil. The milk solids will then sink to the bottom. Lower the heat at this point to have better control over browning the butter.
The milk solids will be yellow and start to caramelize and turn golden in color pretty quickly, so keep an eye on it and make sure to keep stirring or whisking to prevent the milk solids from sticking to the bottom and burning.
Remove the pot from the heat when the brown butter is a shade lighter than the dark golden color that is required.
Use immediately, or pour the butter into a microwave-safe bowl until needed. The butter will continue to darken from the residual heat.
Place the oats in a small food processor. Process the oats until they are finely chopped. This can also be done by a chopper or by manually chopping the oats. Alternatively, you can use quick cook oats or steel cut oats (the same amount by weight). Set aside.
In a large bowl, place the brown and white sugar, salt, flour, zest, and processed oats. Mix together to combine.
Add hot brown butter (or hot melted butter), and vanilla extract. Microwave the brown butter / melted butter for a few seconds to make sure it's heated before adding it (if it has cooled down).
Mix with a rubber spatula until the butter has mixed through with the dry ingredients.
Add 1 tbsp of cream at a time, mixing it in, until the dough is more cohesive. If the dough is warm, it will be very soft. But if it cools down to room temperature it should thicken and form a dough, and that's OK too.
Preheat conventional oven to 350°F / 180°C.
Line a half sheet baking tray with parchment paper or silpat.
Use a tablespoon cookie scoop or a tablespoon measuring spoon to portion out tablespoon-sized dough. Each portion should be about 16 g. To make large cookies, use 1 tbsp sized cookie dough. For smaller cookies, split each tablespoon portion in half (½ tbsp / 8 g each).
Roll each portion in your palms to form a smooth ball.
Place these cookie balls on your lined baking sheet. 5 large cookie dough portions on 1 baking sheet, OR 7 small cookie dough portions on 1 baking sheet. Evenly space them out, as they will spread very thinly and widely in the oven.
If you’re using a light colored metal baking tray, evenly flatten the dough ball with your fingers, or with the bottom of a flat glass. Make sure the flattened cookie is a nice even circle (see pictures in the post for reference).
Bake the cookies in the preheated oven until the cookies are dark golden brown in color, have spread thinly and have bubbles / holes in the middle. 7 - 10 minutes for small cookies, and 10 - 12 minutes for larger cookies. See recipe notes for instructions for dark colored metal pans.
Remove the cookies from the oven and let them cool down slightly before carefully removing the cookies from the sheet pan using a spatula, and placing them on a wire rack to cool down. Let the baking tray cool down.
While the first batch of cookies is baking, portion all of the remaining dough, and have the second tray of cookies ready to go once the first tray comes out. Then once the first baking tray cools down, place cookie dough portions as above, and have it ready to go.
Repeat until all of the dough is baked.
This will make about 20 large oatmeal lace cookies, or about 40 small lace cookies.
You can serve the cookies once they have cooled down.
The cookies do not need to be shaped or trimmed, but if you wish to shape the lace cookies, it must be done while the cookies are still hot and malleable.
To make neat circles, use a clean and sharp cookie cutter that is slightly smaller than the size of the baked lace cookies.
Press down on the cookie with the cookie cutter while it’s still on the baking sheet. Do not twist the cookie cutter, just press it down, and then remove. Once the cookie has cooled, then the edges can easily be trimmed off.
To make cigar or tube shapes, carefully wrap the hot lace cookie around a lightly greased or parchment paper wrapped tube. Press the edges so that the cookie will seal onto itself. Let the cookie cool down on the tube.
Once cooled, the cookie can be removed from the mold.
The cookies can be served as they are.
However, you can drizzle melted chocolate over the surface, or spread melted chocolate on top to make chocolate oatmeal lace cookies, if you like.