Heat the olive oil (1/4 to 1/2 cup depending on your skillet’s size) in a large heavy-bottomed sauté pan over medium-high heat. Once the oil is shimmering, add the onions and fennel and stir to coat.
Keep stirring occasionally for 10 minutes. Add salt and continue to cook for 30 more minutes to an hour, stirring every couple of minutes. You want the onions and fennel to start sticking a little to the pan and getting brown but you’ll want to stir them enough that they don’t burn.
If the onions and fennel are getting really dry or are close to burning you can add a little water to the pan or more olive oil (you can also use broth, wine, or bourbon).
Keep going until the onions and fennel are a rich brown color. Taste and add more salt if needed. Transfer to a bowl and let them come to room temperature.
In a food processor, pulse the goat cheese, 1 tablespoon olive oil, lemon juice, black pepper, and Chinese Five Spice blend until smooth and well blended.
Pulse and blend the caramelized onions and fennel to the cheese mixture a half cup at a time until you like the taste* and the dip is cohesive and smooth. At some times, it will look coagulated, like the oils, solids, and liquids won’t come together.