Pour 1/2 cup water and 1/2 cup champagne into the Instant Pot and insert the steam rack.
Place the lobster tails on the steam rack, then secure the lid, making sure the vent is closed.
Using the display panel select the MANUAL or PRESSURE COOOK function*. Use the +/- keys and program the Instant Pot for 4 minutes.
When the time is up, quick-release the pressure, then remove the lobster tails to a shallow dish and cover with foil. Remove the rack and discard the water
Add 1 tbsp olive oil and 2 tbsp butter to the Instant Pot. Using the display panel select the SAUTE function.
When oil gets hot and butter has melted, add shallots and leeks to the pot and saute until soft, 2-3 minutes. Add garlic and cook for 1-2 minutes more. Add rice and cook for 2-3 minutes more.
Add champagne and stock to the pot and deglaze by using a wooden spoon to scrape any brown bits from the bottom of the pot.
Turn the pot off by selecting CANCEL, then secure the lid, making sure the vent is closed.
Using the display panel select the MANUAL or PRESSURE COOOK function*. Use the +/- keys and program the Instant Pot for 10 minutes.
Meanwhile, melt remaining 2 tsp butter in a small bowl. Crack open lobster shells, pry out the meat and roughly chop. Toss lobster meat with melted butter and 1 tsp lemon juice.
When cooking time is up, quick-release the pressure.
Add mascarpone, salt and while pepper. Stir until desired consistency is reached.
Serve risotto topped with lobster. Sprinkle with fresh thyme.
Glossy grains of arborio rice suspend tender chunks of shellfish within a rich, wine-infused emulsion. Cooking risotto under pressure compresses standard stovetop timing significantly.
Storage and Reheating Guidelines
Seafood risotto degrades rapidly in quality if improperly stored. Cool the dish within two hours and keep it in an airtight container in the refrigerator for up to two days. Freezing is not recommended because the high dairy content in the mascarpone breaks down into a granular texture upon thawing. Reheat refrigerated portions gently in a saucepan over medium-low heat, incorporating two tablespoons of fish stock or water per cup of rice to restore the fluid consistency.
Judging Doneness
Evaluate rice doneness visually and texturally without a thermometer. The grains should display a translucent outer boundary while retaining a chalky, firm center known as al dente. Overcooked pressure-cooked rice loses this structural integrity entirely and turns pasty.
Wine Selection Parameters
Dry sparkling wines provide the necessary acidity to balance the richness of shellfish and butter. Substitute prosecco or cava at a one-to-one ratio if champagne is unavailable. Avoid sweet sparkling wines entirely, as residual sugar distorts the savory balance of the aromatics.