Bring water to a boil in a large saucepan over high heat.

Gradually pour in the cornmeal in a thin stream, whisking continuously. Season with salt.

Reduce the heat to low and stir with a wooden spoon until the mixture is very thick, about 5 minutes.

Remove from the heat and spread as evenly as possible, over a tray covered with parchment paper. Cover with another sheet of parchment paper and allow to set and slightly cool.

With the help of a cookie cutter, cut the polenta into rounds, brush with little olive oil and grill for 2 mins on each sides.

Spread some herby ricotta over the polenta crostini and decorate with arugula, iberian ham, and lemon zest.

Serve immediately at room temperature or chilled. Store in the fridge in an airtight container up to 2 days.