Bring the broth to a boil in a medium saucepan, then reduce the heat and keep at a bare simmer.
Melt 3 tablespoons butter with the olive oil in a large, heavy saucepan over medium heat.
Add the onion and cook, stirring constantly with a wooden spoon, until softened and translucent, about 3 minutes.
Add the rice and cook, stirring, for about 3 minutes, until every grain is coated with butter and oil.
Then add the wine and stir until absorbed.
Add 1 cup of the broth and stir until the liquid is absorbed.
Continue adding broth, about ½ cup at a time, stirring frequently and making sure all the liquid is absorbed before adding more broth.
Cook until the rice is just tender and creamy but still al dente, about 15 to 20 minutes.
You may have leftover broth.
Stir in the asparagus, shrimp, 3 tablespoons butter and lemon zest.
Cook over low heat while stirring until shrimp are heated through and cooked, about 1½ minutes.
Season with salt and pepper, add the fresh thyme, toss well and serve immediately.