Pour the beef stock into a 3-quart / 2.8 L saucepan and bring to a bare simmer over low heat. Keep it there through the whole cook, with a ladle nearby.

Melt half the butter (45 g) with the olive oil in a 28 cm / 11-inch heavy-bottomed saucepan over medium heat. Add the shallot and cook 3 to 4 minutes, stirring, until soft and translucent but not browned.

Add the rice and stir constantly for 2 minutes, until the grains look glassy at the edges and smell lightly toasted.

Pour in 200 ml of the Barolo and stir until it's fully absorbed, scraping up any browned bits from the bottom of the pan.

Start adding the hot stock one ladle at a time, stirring often and waiting until each ladle is mostly absorbed before adding the next. Keep the pot at a steady simmer.

After about 14 minutes, stir in the remaining 80 ml Barolo. This late addition is what keeps the risotto's color deep and ruby instead of pale pink.

Continue adding stock and stirring until the rice is al dente, 17 to 19 minutes total from the first stock addition. Taste at 16 minutes and again at 18, the grain should have a firm bite at the center with no chalky crunch.

Remove the pan from the heat. Beat in the remaining 45 g butter and the grated Parmigiano vigorously with a wooden spoon until the risotto turns creamy and coats the spoon.

If using bone marrow, stir it in now off the heat until it melts into the rice and adds a glossy sheen.

Cover and let the risotto rest for 2 minutes off the heat, then season with salt and pepper. Serve right away in shallow bowls, it should spread slowly into a wave when you tilt the plate.