Trim the asparagus and cut into 1-inch pieces, dice the ham into 1/2-inch cubes, mince the garlic cloves, and measure out the milk, thyme, nutmeg, and both cheeses. Having everything prepped and ready will allow you to build the lasagna quickly without any interruptions once the sauce is made.

Melt the margarine in a skillet over medium heat, then add the minced garlic and cook for about 30 seconds until fragrant. Sprinkle in the flour and stir constantly for 1-2 minutes to create a smooth paste (this is called a roux). Gradually whisk in the milk, stirring constantly to avoid lumps, then add the thyme and nutmeg. Continue simmering for 3-5 minutes, stirring occasionally, until the sauce thickens enough to coat the back of a spoon. I like to add the garlic early in the process so it infuses the entire sauce with flavor rather than just sitting on top.

Since you're using a microwave to finish this dish, I recommend using an 8x8-inch microwave-safe dish or similar size. Spread a thin layer of the béchamel sauce from Step 2 on the bottom, then arrange 3 lasagna noodles (cut in half if needed to fit). Layer with half of the remaining sauce, half of the asparagus, half of the ham, and half of the mozzarella. Repeat with another layer of noodles, the remaining sauce, remaining asparagus, remaining ham, and remaining mozzarella. Top with the parmesan cheese sprinkled evenly across the top. I find that cutting the noodles in half makes them easier to fit in smaller dishes and ensures more even heating.

Cover the lasagna loosely with a microwave-safe lid or paper towel to prevent splattering, then microwave on high for 9-10 minutes until the cheese is melted and the edges are bubbling. Let the lasagna rest for 5-10 minutes before serving—this allows the layers to set slightly and makes it easier to portion without the filling sliding around.