For the rice:
Brush a rimmed baking sheet generously with olive oil and set aside.
Heat broth and keep warm over low flame.
In a deep, heavy-bottomed saucepan heat olive oil over medium flame. Add sausage, breaking into small bits, cooking until golden brown, about 6-8 minutes. Remove sausage with slotted spoon, set aside, leaving the oil and sausage fat in the pan. Add onion to pan and sweat until translucent, stirring occasionally. Add rice and stir until the grains are well-coated, about 3 minutes. Add wine, stirring over medium heat until liquid is almost completely absorbed. Lower flame to medium low and carefully add the broth. Stir briefly, and then let cook until rice is al dente (18-20 minutes), stirring once or twice during that time; the rice grains should tender but still firm.
Remove rice from heat, add the sausage and the cheese, stirring to incorporate thoroughly. Salt to taste
Spread rice in ½” layer on baking sheet and let cool to room temperature. Once cool, cover with plastic wrap; refrigerate from 2 to 24 hours
To form arancini: This portion may be done up to one day ahead
Moisten your palms with cold water (keep a bowl of it next to you)
Roll a very heaping tablespoon of the rice mixture into a ball
Poke a hole in the center of the ball and push a cube of cheese into the hole
Close the hole with a bit more rice
Roll the ball until it is uniformly round, place on a parchment lined baking sheet.
Continue until all the rice and cheese cubes are used
Roll the balls in the bread crumbs, tossing well to coat completely (If doing ahead, cover well with plastic wrap and refrigerate for up to 24 hours. Bring to back to room temperature before frying)
Put oil in a Dutch oven or deep, heavy bottomed pan to heat to 375 degrees F (use candy thermometer). Put the marinara sauce on to warm. Drain on paper towels, sprinkle with seasoning to taste with the chili flakes. Working in small batches, fry the arancini until golden brown, about 3 – 5 minutes. Let arancini cool for a couple of minutes. Serve arancini hot, in a pool warmed marinara (drizzle some over the top of the arancini as well). Sprinkle with grated Dubliner® Cheese, eat immediately with your fingers.