1. Combine masa harina and boiling water in the bowl of a stand mixer. Mix until crumbly and set aside to soften for a few minutes. Combine bread flour, gluten, sugar, salt, and yeast in a small bowl.

2. Pour milk into the bowl with the masa; add flour mixture and lard. Mix on low speed with the dough hook until dough is well combined and clears the sides of the bowl, about 2 minutes. Scrape dough down and mix for 5 minutes more to develop the gluten; dough will be very stiff.

3. Transfer dough to a lightly oiled bowl and cover with plastic wrap. Let rise at room temperature, about 1 1/2 hours. Place butter in the same mixing bowl and use the paddle attachment on low speed to break it up. Mix just until smooth.

4. Scrape butter onto a piece of parchment or waxed paper. Form into a 7-inch square. Cover with another piece of parchment and smooth the top with a rolling pin. Re-form the edges of your square if necessary; a little fussing now will save you some trouble later on as you roll out the dough. Place butter square in the refrigerator to chill.

5. Transfer dough onto a floured work surface. Pat it into a square, transfer to a parchment-lined baking sheet, cover with plastic wrap, and refrigerate for 1 to 24 hours.

6. Remove butter square from the refrigerator about 20 minutes before you plan to roll the dough; it needs to be cool and pliable.

7. Transfer dough onto a floured work surface. Roll it into a square a little larger than the butter square. Leaving a 7-inch square platform in the center for the butter, roll each of the 4 corners of dough out into elongated flaps that can wrap around the butter like a present.

8. Place butter square in the center of the dough, fold up the flaps, and pinch together to seal. Roll dough out into a rectangle. Fold in thirds, like a business letter. Wrap in plastic wrap and refrigerate for 30 minutes.

9. Return dough to the work surface; dust with flour if needed. Roll dough out into a longer rectangle; you're going to do a 4-fold, also called the "book fold." Fold the left edge of the dough into the center of the rectangle; fold the right side in to meet it. Then fold it in half again, like a wallet. Return dough to the parchment-lined baking pan, cover with plastic wrap, and refrigerate for 30 minutes.

10. Place dough on the work surface, roll out into a rectangle again, and make the final turn: another 3-fold, like a business letter. Cover and return to the refrigerator for 30 minutes; the dough can also be frozen at this point.

11. Slice dough in half and return 1 piece to the refrigerator to stay cool. Roll dough out to 1/4-inch thickness. Use a cutter to create 5-inch circles. Transfer circles to a parchment-lined baking sheet and let rise for 1 hour. Shape dough scraps into "tacro cups" and place in the cups of a muffin tin; let rise. Repeat both steps with remaining dough.

12. Heat oil in a deep-fryer or large saucepan to 350 degrees F (175 degrees C). Gently fold a dough circle in half to form a taco shell shape; holding it with tongs, lower it into the oil. Hold it closed for about 10 seconds. Fry 2 shells at a time until golden, turning once, about 3 minutes total. Repeat with remaining dough circles, maintaining the oil heat between 350 and 375 degrees F (190 degrees C). Drain tacro shells on paper towels.

13. Preheat the oven to 375 degrees F (190 degrees C).

14. Bake tacro cups in the muffin tin until golden, 15 to 18 minutes. Fill cups and shells with your favorite taco fillings.

Cook's Notes:

This recipe yields about 10 tacro shells (rounds) and 12 tacro cups (made with scraps) baked in muffin tins. I used 6 ounces of masa meal and 12 ounces of bread flour. If you want a lighter-textured croissant, reduce the masa to 2 ounces (1/2 cup) and replace it with bread flour. Omit the vital wheat gluten as well. Avoid re-rolling the dough, since it'll mash together all those beautiful layers you worked so hard to create.

After the final fold, you can wrap the dough in plastic wrap and aluminum foil and freeze. Thaw, still wrapped, in the fridge overnight. Proceed as directed in Step 11.

You can use an empty 24-ounce can or a large jar lid as a cutter. Like biscuits, though, the sharper the edge of the cutter, the higher the dough will rise and the more flaky layers you'll get.

You can also bake the tacro shells, instead of frying them. Use folded heavy-duty aluminum foil to make a ridged mold that will hold the dough circles upside down while they bake. Set the foil mold on a baking sheet. Gently bend the circles into taco shell shapes, drape them over the foil, and let rise at room temperature for 1 hour. Bake along with the cups.

Editor's Note:

We have determined the nutritional value of oil for frying based on a retention value of 10% after cooking. Amount will vary depending on cooking time and temperature, ingredient density, and specific type of oil used.