Fill a pot with water and bring it to a boil. Salt it well and add your pasta. Cook until al dente.
Meanwhile, in a skillet, braiser, sauté pan or wok, melt a large knob of butter in olive oil. Add the shallots and sauté gently for a minute or so, until the shallot softens without browning, seasoning with a pinch of salt.
Add the smoked salmon and sauté until it has turned color, then add the peas.
Turn everything around for another minute, then add the heavy cream. Let the heavy cream reduce until it has reached a sauce-like consistency that will coat a spoon. Taste and adjust for seasoning.
When the pasta is cooked, transfer it to the pan with the salmon and pea sauce, along with a small ladleful of the pasta cooking water.
Raise the heat and toss everything together over a lively flame until the pasta and sauce are well mixed and the sauce coats the pasta nicely.
Serve immediately.