Soak 10 g dried morels in 100 ml lukewarm water for 1 hour.
Peel and finely dice 1 onion.
Remove morels from soaking water and rinse under running water.
Strain the morel soaking water through a fine sieve into a bowl (discard any grit).
Reserve 2 whole morels for garnish; finely dice the remaining morels.
Flatten the beef fillet slices by hand.
Season the flattened fillets with salt and pepper from the grinder.
Heat a skillet over medium-high heat and fry the beef fillets for 2-3 minutes per side until medium-rare (55 °C / 130 °F), then set aside on a warm plate.
In the same skillet over medium heat, sauté the diced onion for 4-5 minutes until translucent.
Add the diced morels and deglaze the pan with 50 ml brandy.
Pour in 100 ml white wine, the strained morel soaking water, ¼ cube gravy, and 100 ml cream.
Simmer for 5-8 minutes until the sauce thickens.
Place the warm beef fillets on warm plates, top with the morel cream sauce, garnish with the reserved morels, and serve with side dishes.