Start by slicing your yellow onions, red onions, and shallots into uniform ¼-inch thick slices. This uniform thickness ensures even cooking—some pieces won't burn while others remain raw. I use a mandoline for consistency, which saves about 10 minutes of knife work and reduces hand fatigue. Keep the onions in separate piles initially because we'll add them in stages for optimal texture. Remove any papery outer layers and rinse under cool water to remove excess sulfur compounds that can create bitterness.

Heat your olive oil and grass-fed butter together in a large, heavy-bottomed skillet over medium heat. Once the butter is foaming (about 1 minute), add your yellow onions and ½ teaspoon kosher salt. Do not increase the heat—this is the most common mistake I see. High heat creates brown onions, not caramelized ones. You want a gentle, steady process that takes 25-30 minutes total. Stir the onions every 2-3 minutes for the first 10 minutes, then allow them to sit undisturbed for 2-3 minutes at a time. This "rest and stir" method creates the caramelization you're after. The onions will go through phases: first they'll release water and become translucent (5-7 minutes), then they'll start sticking slightly to the pan (this is good—those are the flavorful browned bits), and finally they'll turn a deep golden amber color.

After the yellow onions have caramelized for about 15 minutes and turned that beautiful golden color, add your red onions and shallots along with the remaining ½ teaspoon salt. Red onions caramelize faster than yellow onions because of their higher natural sugar content, so timing this addition ensures everything finishes together. Stir well and continue the low heat cooking process for another 10-12 minutes. You'll notice the onions deglaze the pan and become slightly wetter—this is normal. Keep stirring occasionally. The final 3-4 minutes are crucial: resist the urge to stir constantly. Allow the onions to sit for a full minute or two so the bottom layer makes contact with the hot pan and develops those caramelized, slightly crispy edges. Those crispy bits are pure umami flavor.

Add your minced garlic and fresh thyme (if using) during the final minute of cooking. The residual heat will gently cook the garlic without burning it. Add your balsamic vinegar and stir thoroughly for about 20 seconds. The acid will deglaze any stuck-on bits and add subtle sweetness that complements the caramelized onions beautifully. Taste and adjust salt and pepper as needed. Remove from heat and allow the mixture to cool for 5 minutes. This brief resting period lets the flavors marry and makes the mixture easier to handle when topping your pizza.

While your onions are caramelizing, preheat your oven to 425°F. If you're using a store-bought crust, place it on your pizza stone or parchment-lined baking sheet. If you're making your own, this is when you'll shape it. Don't stretch the dough aggressively—gentle shaping maintains the air pockets that create a lighter, airier crust. Mix your part-skim mozzarella and ricotta together in a small bowl until roughly combined. This creates a creamy base that won't dry out during baking. Ricotta has a much higher water content than mozzarella, but that's actually an advantage here—it keeps the crust from becoming tough while delivering more protein per ounce.

Spread the ricotta-mozzarella blend evenly across your crust, leaving about ½ inch around the edges for browning. Don't overload the base—you want roughly 2-3 tablespoons of cheese blend per slice. This might seem light compared to traditional pizza, but the intense caramelized onions will make every bite feel indulgent. Top evenly with your caramelized onion mixture, spreading it in an even layer. Finish with a light sprinkle of Parmigiano-Reggiano (about 2 tablespoons total). This hard Italian cheese adds intense savory notes that compensate for using less total cheese. Bake at 425°F for 14-16 minutes until the crust is golden and the cheese is bubbling at the edges. Remove and let cool for 2-3 minutes before slicing. This brief rest allows the cheese to set slightly so each slice holds together beautifully.