Preheat oven to 375 degrees F (190 degrees C). Line insulated baking sheet with parchment paper.
Sift together flour, baking powder and salt.
Cream together the butter and sugar. Add the egg yolks and vanilla, beating until light and fluffy. Mix in the dry ingredients. If your dough is sticky, refrigerate it for 1 hour to make it easier to work with.
Shape into 1 inch balls (about 1 tablespoon each). Push a skewer or the end of a wooden spoon all the way through center of each ball and shape dough into a ring. Make sure the whole is big enough as these cookies double in size and the hole will close up while baking. Dip top of each ring in sprinkles. Place cookies onto the prepare baking sheets.
Bake at 375 degrees F (190 degrees C) for 10 to 12 minutes or until light golden brown. DON'T OVER BAKE. 8 minutes was perfect for mine. Remove from the baking sheets and let cool on racks.
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Notes
These Mexican Cookie Rings do bake up quite a bit. Make sure you leave enough room between cookies on the cookie sheet.
Be careful with the butter. Take it out of the fridge and let it sit on the counter for about 20 minutes. Press your finger into the butter. It should yield slightly and leave a small dent. That's the correct texture. If your finger creates a larger indent or goes through the butter, your dough will be sticky and difficult to work with.
This dough makes 25-30 cookies, depending on your interpretation of a teaspoon. A scant teaspoon will yield about 30-31 cookies.
As noted in the instructions below, be sure the hole in the cookie is big enough. These cookies expand and if the hole is too small, it will close up.